DEPARTMENT  OF  THE  INTERIOR 
UNITED  STATES  RFCI  "M'.TION  SERVICE 


MEASUREMENT  of 
IRRIGATION  WATER 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1918 


DEPARTMENT  OF  THE  INTERIOR 

UNITED  STATES  RECLAMATION  SERVICE 


MEASUREMENT  of 
IRRIGATION  WATER 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1918 


MEASUREMENT  OF  IRRIGATION  WATER. 


INTRODUCTORY   STATEMENT. 

1.  Importance  of  -measurement. — Accurate  measurement  of  irri- 
gation water  is  of  fundamental  importance  to  good  irrigation  man- 
agement. A  perfect  understanding  of  some  of  the  primary^  principles 
relating  to  the  subject  of  water  measurement  is  therefore  necessary. 
For  the  purpose  of  furthering  an  understanding  of  these  principles 
and  for  the  purpose  of  having  information  and  tables  on  the  subject 
convenient  for  field  use,  this  booklet  was  compiled  in  1913  by  F.  W. 
Hanna.^ 

2.  General  units  of  measurement. — The  units  of  measurement 
at  present  employed  in  irrigation  practice  in  the  West  are  the  miner's 
inch,  the  second-foot,  and  the  acre-foot.  The  miner's  inch  is 
not  a  definite  unit,  varying  as  to  quantity  in  the  different  States. 
Fifty  miner's  inches  are  equivalent  to  i  second-foot  in  Idaho, 
Kansas,  Nebraska,  New  Mexico,  North  Dakota,  and  South  Dakota. 
In  Arizona,  California,  Montana,  and  Oregon,  40  miner's  inches  are 
equivalent  to  i  second-foot,  while  in  Colorado,  38.4  miner's  inches 
are  equivalent  to  i  second-foot.  A  second-foot  is  that  unit  of  flow 
that  will  produce  i  cubic  foot  of  volume  in  one  second  of  time.  An 
acre-foot  is  that  imit  of  quantity  required  to  cover  i  acre  of  land 
I  foot  in  depth.  It  should  be  noted  that  the  element  of  time  enters 
into  the  miner's  inch  and  into  the  second-foot,  but  that  the  acre- 
foot  does  not  involve  the  element  of  time. 

3.  Units  of  measure  adopted. — Owing  to  the  fact  that  the  miner's 
inch,  made  definite  by  the  use  of  the  second-foot  as  a  unit,  has  a 
different  value  in  different  States,  it  is  an  undesirable  unit  of  meas- 
ure to  use,  and  the  ser\dce  has  adopted  the  second-foot  as  the  unit 
of  measure  where  flow  is  considered.  Owing  to  convenience  of 
size  and  its  particular  application  to  land  areas,  the  acre-foot  has 
been  adopted  as  the  unit  of  measure  where  volume  is  considered 
independently  of  time. 

4.  Kinds  of  measuring  devices. — In  the  measiu-ement  of  irrigation 
water  the  service  has  adopted  weirs,  submerged  orifices,  and  current- 
meter  gaging  stations.  Where  there  is  sufficient  available  fall,  and 
the  quantity  of  water  to  be  measured  is  not  too  large ,  the  most  service- 
able and  economical  measuring  device  that  can  be  used  is  the  weir; 
where  there  is  little  available  fall,  the  quantity  of  water  is  small 

'  The  text  of  the  1913  edition  has  been  used  unchanged. 


4  MEASUREMENT   OF   IRRIGATION    WATER. 

and  there  is  not  too  much  floating  debris,  the  submerged  orifice  is 
applicable;  where  the  quantit}^  of  water  is  large  and  there  is  not 
available  sufficient  fall  for  the  use  of  a  weir,  current-meter  gaging 
stations  are  applicable.  These  three  methods  of  measuring  irrigation 
water  are,  therefore,  supplemental  to  one  another  in  covering  the 
entire  field  of  need. 

PART   I.  WEFRS. 

5.  Definition  and  classification  of  weirs.- — A  weir  may  be  defined 
as  a  notch  in  the  top  of  a  vertical  wall  through  which  water  flows. 
The  determination  of  the  quantity  of  water  that  v/ill  flow  through 
such  a  notch  under  specific  conditions  depends  upon  experimental 
data  taken  in  connection  with  the  cross-sectional  area  of  the  dis- 
charge sheet  through  the  notch.  The  weirs  generally  employed 
for  the  measurement  of  irrigation  water  are  the  trapezoidal  weir  of 
the  Cippoletti  type  and  the  rectangular  weir.  Each  of  these  types 
inay  again  be  divided  into  free  weirs  and  submerged  weirs.  The 
free  weir  is  one  in  which  the  water  elevation  on  the  downstream  side 
of  the  weir  does  not  reach  up  to  the  elevation  of  the  weir  crest.  The 
submerged  weir  is  one  in  which  the  water  elevation  on  the  down- 
stream side  of  the  weir  rises  to  an  elevation  above  the  crest  of  the 
weir.  Weirs  are  also  classified  as  suppressed  or  contracted  weirs. 
The  contracted  weir  is  one  with  its  sides  so  far  removed  from  the 
sides  of  the  channel  that  the  filaments  of  water  are  fully  contracted 
as  the  water  passes  through  the  weir.  The  suppressed  weir  is  one 
with  its  sides  coincident  with  the  sides  of  the  channel,  so  that  the 
filaments  of  water  pass  through  the  weir  without  being  deflected 
from  their  normal  course . 

6.  Types  of  weirs  adopted.- — The  type  of  weirs  adopted  by  the 
service  for  the  meiisurement  of  irrigation  water  are  the  sharp-crested 
and  sharp-sided  contracted  rectangular  weir,  the  sharp-crested 
suppressed  rectangular  weir,  and  the  sharp-crested  and  sharp-sided 
Cippoletti  weir.  These  three  types  of  weir  will  be  hereinafter 
designated,  respectively,  as  the  standard  contracted  rectangular 
weir,  the  standard  suppressed  rectangular  weir,  and  the  standard 
Cippoletti  weir.  It  is  the  aim  of  the  service  to  use  these  weirs  without 
submergence,  although  there  may  be  cases  where  it  will  be  necessary 
to  permit  submergence  for  short  periods  at  least. 

7.  Definition  and  conditions  for  accuracy  of  standard  contracted 
rectangular  weirs. — A  standard  contracted  rectangular  weir  is  a 
rectangular  weir  wnth  its  crest  and  sides  consisting  of  a  thin-edged 
plate  and  so  far  removed,  respectively,  from  the  bottom  and  sides 
of  the  leading  channel  as  to  cause  the  filaments  of  water  to  be  fully 
deflected  from  their  normal  course.  The  deflection  is  approximately 
the  maximum  deflection  that  would  obtain  with  the  crest  and  sides 
of  the  weir  at  imlimited  distajices  from  the  channel  boimdaries. 


WEIRS.  5 

The  crest  and  sides  may  be  made  of  planks  if  the  upstream  edges  are 
definite  rectangular  corners,  but  it  is  best  to  use  a  thin  metal  plate. 
Several  extended  series  of  experiments  have  been  conducted  for 
determining  the  proper  coefficient  to  apply  to  the  contracted  weir 
of  the  type  here  discussed  and  to  establish  conditions  that  insure 
perfect  contraction.  As  a  result  of  these  experiments,  the  following 
conditions  are  considered  necessary  for  accuracy  of  measurements: 

(a)  The  upstream  crest  and  side  edges  of  the  weir  should  be  sharp 
and  smooth,  and  the  distance  of  the  crest  and  sides  respectively  from 
the  bottom  and  sides  of  the  leading  channel  should  preferably  be  not 
less  than  twice  the  depth  of  water  on  the  weir,  and  in  no  ease  be  less 
than  I  foot. 

(6)  The  overflowing  sheet  should  touch  only  the  upstream  edges 
of  the  crest  and  sides. 

(c)  Air  should  circulate  freely  both  under  and  on  the  sides  of  the 
overflowing  sheet. 

(d)  The  upstream  face  of  the  weir  should  be  vertical. 

(e)  The  crest  should  be  level  from  end  to  end. 
(/)  The  sides  should  be  truly  vertical. 

(g)  The  measurement  of  head  on  the  weir  should  be  the  actual 
elevation  of  the  water  surface  above  the  level  of  the  weir  crest,  and 
should  be  taken  from  4  to  lo  feet  upstream  from  the  weir. 

(k)  The  cross-sectional  area  of  the  leading  channel  for  20  to  30  feet 
upstream  from  the  weir  should  be  at  least  six  times  that  of  the 
overflowing  sheet  at  the  weir  crest. 

(i)  Corrections  should  be  made  for  velocity  of  approach  where 
appreciable  errors  are  caused  by  neglecting  the  head  due  to  it. 

8.  For->nulas  for  standard  contracted  rectangular  weir'. — Two  widely 
used  formulas  for  computing  the  discharges  over  standard  contracted 
rectangular  weirs  are  those  of  Hamilton  Smith  and  J.  B.  Francis. 
The  formulas  proposed  by  Hamilton  Smith  require  the  use  of  coeffi- 
cients of  discharge  varying  with  the  head  of  water  on  the  weir,  and 
also  with  the  length  of  v/eir,  which  makes  them  somewhat  incon- 
venient, although  they  are  accurate  for  the  ranges  of  coefficients 
usually  given.  The  Francis  formula  for  this  type  of  weir  without 
velocity  of  approach  is  as  follows: 

(i)     C?=3-33HML-o.2//); 
and  with  velocity  of  approach  is  as  follows: 

(2)     S^=3-33[(^+A)^-A']  (L-0.2  H); 

in  which  0  is  the  discharge  in  second-feet  without  velocity  of 
approach;  O'  the  discharge  in  second-feet  with  velocity  of  approach; 
L  the  length  of  weir,  in  feet;  H  the  head  on  the  weir,  in  feet;  and  h 
the  head  due  to  velocity  of  approach,  in  feet.  It  will  be  noted 
that  the  Francis  formulas  contain  constant  discharge  coefficients, 


6  MEASUREMENT  OF  IRRIGATION   WATER. 

which  make  computations  by  them  easy  without  the  use  of  tables. 
The  Francis  experiments  were  made  on  comparatively  large  weirs, 
most  of  them  lo  feet  long,  with  heads  ranging  from  0.4  to  1.6  feet, 
so  that  the  formulas  apply  particularly  to  such  weirs  rather  than  to 
short  Aveirs  with  low  heads.  Experiments  on  6-inch,  i-foot,  2-foot, 
and  3-foot  weirs  on  the  Boise  project,  Idaho,  show  that  these  formu- 
las apply  fairly  well  to  shorter  weirs,  provided  the  head  of  water  on 
the  weir  is  not  greater  than  about  one-third  the  length  of  the  weir. 
For  a  ratio  of  depth  to  length  greater  than  this  the  actual  discharges 
exceed  those  given  by  the  formulas  by  an  amoimt  which  increases 
gradually  from  about  o  per  cent  for  a  ratio  of  3-^  to  about  30  per  cent 
for  a  ratio  of  1 . 

9.  Definition  and  conditions  for  accuracy  of  standard  suppressed 
rectangular  weir. — A  standard  suppressed  rectangular  weir  is  a  rec- 
tangular weir  with  its  crest  consisting  of  a  thin  plate  so  far  removed 
from  the  bottom  of  the  leading  channel  as  to  cause  the  filaments  of 
water  to  be  fully  deflected  from  their  normal  course,  and  with  its 
sides  coincident  with  the  sides  of  the  leading  channel,  so  that  there 
is  no  change  in  direction  laterally  of  the  filaments  of  water  passing 
through  the  weir.  All  conditions  for  accuracy  of  measurements  for 
this  type  of  weir  are  identical  with  those  of  the  contracted  rectangu- 
lar weir,  except  those  relating  to  side  contraction.  In  the  suppressed 
weir  the  sides  of  the  leading  channel  should  be  coincident  with  the 
sides  of  the  weir,  and  the  over-falling  sheet  should  not  be  allowed 
to  expand  immediately  downstream  from  the  weir.  Special  care 
must  be  taken  in  this  type  of  weir  to  secure  the  proper  aeration 
beneath  the  overflowing  sheet  below  the  crest. 

10.  Formulas  for  standard  suppressed  rectangular  weir. — The  two 
principal  formulas  used  for  computing  the  discharge  of  the  standard 
suppressed  rectangular  weirs  are  also  those  of  Smith  and  Francis. 
In  the  Smith  formulas  for  suppressed  weirs,  as  for  contracted  weirs, 
the  coefficients  of  discharge  var>-  with  the  head  on  the  weir  and  with 
the  length  of  the  weir,  so  these  formulas  are  not  convenient  for  com- 
putations without  the  use  of  tables  of  coefficients.  The  law  of  these 
variations  for  the  two  types  of  weirs  is  different,  so  it  is  necessary  to 
provide  a  separate  table' for  each.  The  Francis  formula  for  the  stand- 
ard suppressed  rectangular  weir  without  velocity  of  approach  is  as 
follows: 

(3)     Q=Z-ZZLHh 
and  with  velocity  of  approach  is  as  follows: 

(4)     G^=3-33^  [{H+h)i-hn. 
In  these  formulas  the  letters  have  the  same  significance  as  in  those 
for  contracted  weirs,  and  the  coefficient  of  discharge  was  obtained  by 
Francis  from  the  same  general  set  of  experiments  as  those  stated  for 


WEIRS.  7 

the.  contracted  weir.  No  extensive  tests  have  been  made  to 
determine  the  applicability  of  these  formulas  to  weirs  less  than  4  feet 
in  length. 

n.  Definition  and  conditions  for  accuracy  of  standard  Cippoletti 
weir. — A  standard  Cippoletti  weir  is  a  trapezoidal  weir  with  its 
crest  and  sides  consisting  of  a  thin  plate,  and  so  far  removed  from 
the  bottom  and  sides  of  the  leading  channel  as  to  cause  the  filaments 
of  water  to  be  deflected  from  their  normal  course  and  with  its  sides 
sloping  outward  as  they  rise  in  a  ratio  of  i  to  4.  While  this  weir  is 
necessarily  a  contracted  weir,  and  should  be  so  considered  as  far  as 
requirements  of  installation  are  concerned,  yet,  in  discharge  effect, 
it  is  a  suppressed  weir.  This  is  due  to  the  fact  that  Cippoletti  in 
his  formula  has  allowed  for  the  reducing  effect  in  the  discharge  due 
to  end  contractions  b)'^  making  the  sides  of  the  weir  sufficiently 
sloping  to  overcome  this  effect.  All  conditions  for  accuracy  stated 
for  the  standard  contracted  rectangular  weir  apply  to  the  Cippoletti 
weir  except  that  of  the  slope  of  the  sides. 

12.  Formulas  for  standard  Cippoletti  weir. — Theoretically  the 
formula  for  the  standard  Cippoletti  weir  without  velocity  of  approach 
should  be  the  same  as  the  Francis  formula  for  the  standard  sup- 
pressed rectangular  weir.  Cippoletti,  from  his  experiments,  how- 
ever, increased  the  Francis  coelffcient  by  about  i  per  cent,  so  that 
his  formula,  without  velocity  of  approach,  is  as  follows: 

(5)  2=3.367  LH^: 

The  discharge  for  this  weir  with  velocity  of  approach  may  be  ob- 
tained from  the  following  formula: 

(6)  2^=3.367  L(//-f  1.5  A)f 

In  these  formulas  the  letters  have  the  same  significance  as  in  the 
preceding  formulas.  The  correction  for  velocity  of  approach  may 
be  applied  as  in  the  Francis  formula  also  with  fair  results. 

13.  Velocity  of  approach  in  weir  measurements . — So  far  as  practi- 
cable weirs  should  be  installed  so  as  to  make  the  velocity  of  approach 
negligible;  but  where  it  is  impracticable  to  do  this  appropriate 
corrections  should  be  made.  vSuch  corrections  for  the  Francis 
formulas  are  difficult  to  make  without  the  use  of  tables  providing 
percentages  of  increase  to  apply  to  the  computed  discharges.  In 
the  formula  given  for  use  with  the  Cippoletti  weir  the  correction  can 
be  applied  to  the  measured  head  directly  and  the  proper  discharge 
readily  obtained,  or  the  discharge  can  be  obtained  as  indicated  by 
the  Francis  method  and  use  of  tables.  Attention  is  called  to  the 
fact  that  moderate  velocities  of  approach  with  low  heads  on  the 
weir  produce  large  errors,  whereas  comparatively  high  velocities  of 


3k  MEASUREMENT  OF   IRRIGATION   WATER. 

approach  with  large  heads  on  the  weir  produce  relatively  small 
errors.  The  velocity  of  approach  may  be  computed  from  the  follow- 
ing formula: 

(7)  v=Q^A; 

in  which  t;  is  the  velocity  of  approach  in  feet  per  second,  Q  the  dis- 
charge in  second-feet,  and  A  the  cross-sectional  area  of  the  leading 
channel  in  square  feet.  The  discharge  may  be  computed  by  the 
appropriate  weir  formula  without  velocity  of  approach,  with  suffi- 
cient accuracy  for  determining  v  for  ordinary  cases.  Successive 
approximations  may  be  used  to  determine  -v  to  any  desired  degree 
of  accuracy  for  special  cases.  Having  obtained  the  value  of  v,  the 
velocity  of  approach  head  may  be  computed  from  the  following 
formula: 

(8)  /t=o.ois6  v^. 

After  h  has  been  computed  from  formula  (8),  the  effective  head,  D, 
on  the  weir  can  be  computed  from  the  measured  head,  H,  by  means 
of  the  following  formula: 

(9)  D=[{H+hy'-h^i■, 

in  which  H  and  h  have  the  same  significance  as  in  preceding  formulas, 
and  D  is  the  effective  head  due  to  the  measured  head  and  velocity 
of  approach.  The  weir  discharge  is  then  given  by  the  proper  formula 
for  each  type.of  weir  as  hereinbefore  given.  For  any  type  of  weir,  if 
the  Francis  method  of  correcting  for  velocity  of  approach  is  used  by 
comparing  formula  (2)  to  formula  (i),  or  formula  (4)  to  formula  (3), 
it  is  seen  that  the  increased  discharge  with  velocity  of  approach 
bears  to  the  discharge  for  the  same  weir  and  head  without  velocity 
of  approach  the  ratio  shown  in  the  following  formula: 

(10)  ^=— j=C; 
Q     H^ 

in  which  Q^,  Q,  H,  and  D  have  the  same  significance  as  in  preceding 
formulas  and  C  is  a  ratio  varying  with  H  and  the  velocity  of  approach. 
It  is  obvious  that  C  applied  as  a  coefficient  to  Q  will  give  Q  . 

14.  Suhnergence  0/  weirs. — Accurate  measurement  can  not  be  made 
of  submerged  weir  discharges,  on  account  of  lack  of  extensive  accu- 
rate experiments  for  determining  the  discharge  coefficient.  Practi- 
cally all  of  the  older  experiments  on  submerged  weirs  were  on  sup- 
pressed rectangular  ones.  Clemens  Herschel,  from  a  discussion  of 
these  experiments,  derived  a  formula  for  computing  discharges  for 
such  weirs.     The  Herschel  formula  is  as  follows: 

(11)  e,=3-33^("^^)''; 


WEIRS.  9 

in  which  L  and  H  have  their  usual  significance,  as  applied  to  a  free 
suppressed  rectangular  weir,  Q^  is  the  discharge  in  second-feet  with 
submergence,  and  n  is  a  factor  of  correction  taken  from  a  table  for 
varying  values  of  the  ratio  of  submergence,  (d-i-H),  d  being  the 
downstream  head  and  H  the  upstream  head  on  the  weir,  both  in 
feet.  Recently,'  limited  experiments  have  been  made  on  sub- 
merged contracted  weirs  by  J.  C.  Stevens,  on  the  Sunnyside  project 
of  the  service.  These  experiments  were  considered  and  combined 
by  Stevens  with  the  older  ones  and  a  diagram  prepared  for  determin- 
ing the  discharges  of  submerged  weirs,  both  contracted  and  sub- 
pressed,  from  appropriate  tables  of  free  weirs.  These  results  differ 
only  slightly  from  those  of  Herschel,  so  it  may  be  roughly  con- 
sidered that  Herschel 's  coefficients  apply  approximately  to  con- 
tracted as  well  as  to  suppressed  weirs.  In  Herschel 's  formula  the 
coefRcient  n  is  applied  to  the  observed  head  above  the  weir  crest  on 
the  upstream  side.  By  comparing  formula  (ii)  to  formula  (3),  the 
corresponding  formula  without  submergence,  it  is  seen  that  accord- 
ing to  Herschel 's  formula  the  discharge  of  a  submerged  weir  bears  to 
that  of  a  free  weir  with  the  same  length  and  head  the  ratio  shown  in 
the  following  formula: 

^     '     Q        H^  ' 

in  which  Qi,  Q,  H  and  n  have  the  same  significance  as  in  preceding 
formulas  and  C^  is  a  ratio  varjdng  with  ?i  or  with  the  ratio  of  sub- 
mergence.    It  is  obvious  that  C^  applied  as  a  coeflicient  to  Q  will 

15.  Construction  of  weirs. — Weir  boxes  should  be  substantially 
constructed  of  lumber  or  concrete.  The  weir  box  should  in  all 
cases  extend  downstream  from  the  weir  crest  far  enough  to  still 
the  water  before  it  passes  back  into  the  earth  channel  below.  The 
floor  of  this  downstream  portion  of  the  box  may  well  be  slightly 
depressed  to  form  a  stilling  pool;  the  sides  should  be  coincident 
with  the  overflow  sheet  for  suppressed  weirs,  and  should  be  set 
back  slightly  from  the  sides  of  the  weir  crest  for  contracted  weirs. 
In  suppressed  weirs  a  pipe  or  other  means  should  be  provided  for 
admitting  air  to  the  underside  of  the  overfalling  sheet  in  order  to 
assure  accurate  contraction.  The  weir  baseboard  might  well  be 
made  removable,  so  that  the  silt  accumulating  in  the  weir  pool 
can  be  flushed  out  from  time  to  time.  In  cases  of  suppressed  weirs 
the  weir  box  should  be  extended  upstream  several  feet  in  order  to 
insure  perfect  suppression  of  the  end  contractions.  The  crest  of 
the  weir  in  any  case  should  be  placed  sufficiently  high  above  the 
bed  of  the  canal  to  insure  perfect  crest  contraction.     The  sides  of 

1  The  text  of  the  1913  edition  has  been  used  unchanged. 
57737—18 2 


lO  MEASUREMENT   OF   IRRIGATION    WATER. 

contracted  weirs  should  likewise  be  built  sufficiently  far  from  the 
sides  of  the  channel  to  permit  of  perfect  end  contractions.  Wing- 
walls  or  cut-off  walls  should  be  extended  into  the  banks  of  the  canal, 
both  at  the  upper  and  lower  end  of  the  weir  box,  for  the  purpose 
of  preventing  leakage  around  the  box,  and  for  preventing  back- 
cutting  at  the  canal  banks. 

i6.  Installation  of  weirs. — The  weir  box  should  be  installed  suffi- 
ciently far  from  the  turnout  to  permit  of  constructing  a  pool  of  the 
required  length  for  stilling  the  water  before  passing  through  the 
weir.  The  leading  channel  or  weir  pool  should  be  made  with  uni- 
form dimensions,  and  of  the  required  length  to  give  proper  approach 
and  contraction  of  the  water.  The  weir  box  should  be  carefully 
leveled  in  both  directions  at  the  time  of  installation.  The  weir 
crest  should  be  accurately  leveled  and  the  sides  of  the  weir  set  to 
the  required  slopes  for  the  type  of  weir  being  installed.  The  struc- 
ture should  be  carefully  puddled  to  prevent  the  passing  of  water 
around  or  underneath  it.  There  should  be  substantialh*  installed 
a  metallic  gage  reading  to  hundredths  of  a  foot,  located  sufficiently 
far  above  the"  weir  crest  to  be  out  of  the  effect  of  the  draw-down  at 
the  weir  crest.  This  gage  should  be  accurately  installed  with  its 
zero-point  at  the  same  elevation  as  that  of  the  weir  crest,  and  at  a 
convenient  location  for  checking  these  elevations  from  time  to 
time.  Where  the  elevation  of  the  water-surface  in  the  canal  is  low 
in  comparison  with  adjacent  land  to  be  irrigated,  and  where  there 
is  but  little  fall  in  the  land,  extra  precaution  should  be  taken  to 
prevent  submergence  of  the  weir. 

17.  Care  of  weirs. — The  weir  and  weir  pool  should  be  freed  from 
weeds  and  trash  at  each  round  of  the  canal  rider  and  the  weir  pool 
should  be  cleaned  of  silt  from  time  to  time  as  it  accumulates.  The 
level  of  the  crest  should  be  checked  from  time  to  tim.e,  and  should 
also  be  checked  with  reference  to  the  elevation  of  the  zero  of  the 
gage.  Inspection  should  be  made  to  determine  whether  there  is 
leakage  around  the  weir,  and  in  the  event  of  such  leakage  the  struc- 
ture should  be  immediately  repuddled  and  carefully  rechecked  to 
see  that  the  crest  is  level  and  at  the  elevation  of  the  zero  of  the  gage. 

18.  Table  i. — This  table  contains  discharges  in  second-feet  for 
standard  contracted  rectangular  weirs  without  velocity  of  approach, 
computed  from  the  Francis  formula  for  the  lengths  and  heads  ordi- 
narily used  in  measuring  small  quantities  of  irrigation  water;  except 
that  for  the  6-inch,  i-foot,  2-foot,  and  3-foot  weirs,  for  heads  greater 
than  one-third  the  crest  length,  the  experimental  values  obtained 
on  the  Boise  project  have  been  used  instead  of  the  values  given  by 
the  formula.  This  table  may,  therefore,  be  considered  to  give 
fairly  accurate  discharges  for  weirs  of  the  above-stated  lengths  and 
for  w-eirs  of  other  lengths  where  the  head  does  not  exceed  one-third 
the  length  of  the  weir  crest.  The  method  of  using  the  table  is 
apparent. 


WEIRS.  II 

19.  Tabk  2. — This  table  contains  discharges  in  second-feet  for 
standard  Cippoletti  weirs  withovit  velocity  of  approach,  computed 
from  the  Cippoletti  formula  for  the  heads  and  lengths  of  weirs  gener- 
ally used  in  measuring  small  quantities  of  irrigation  water;  except 
that  for  the  6-inch,  i-foot,  2-foot,  and  3-foot  weirs,  for  heads  greater 
than  one-third  the  crest  length,  the  discharges  have  been  taken  from 
experiments  made  on  the  Boise  project.  The  data  should,  there- 
fore, be  considered  fairly  accurate  for  weirs  of  the  above-stated 
lengths  for  all  heads  given  in  the  table  and  for  weirs  of  other  lengths 
for  heads  not  over  one-third  the  crest  length.  This  table  is  applicable 
also  to  standard  suppressed  rectangular  weirs,  as  indicated  in  para- 
graph 12. 

20.  Table  j. — Table  3  gives  coefficients,  which,  applied  to  the 
discharges  taken  from  Table  i  or  2 ,  will  give  the  discharges  for  the 
same  weirs  when  velocity  of  approach  exists.  When  there  is  con- 
siderable velocity  of  approach,  corrections  should  be  made  by 
means  of  this  table.  For  this  purpose  the  velocity  of  approach 
should  first  be  computed  as  hereinbefore  described.  The  discharge 
without  velocity  of  approach  should  then  be  taken  from  Table  i  or 
2  and  Multiplied  by  the  coefficient  given  in  Table  3. 

Illustration:  Suppose  it  is  desired  to  find  the  discharge  of  a 
standard  suppressed  rectangular  weir  with  a  crest  length  of  6  feet 
under  a  measured  head  of  2.5  feet  and  when  there  is  a  mean 
velocity  of  approach  determined  to  be  1.5  feet  per  second.  By 
Table  2  the  discharge  without  velocity  of  approach  is  79.85  second- 
feet.  From  Table  3,  for  a  velocity  of  approach  of  1.5  feet  per 
second  and  with  a  head,  H,  of  2.5  feet,  the  coefficient  is  1.019. 
79.85  X  1. 019  =  81.367  second-feet  discharge  with  velocity  of 
approach. 

21.  Table  4. — Table  4  gives  coefficients,  which,  when  applied  to 
the  discharge  of  a  weir  as  taken  from  either  Table  i  or  2,  will  give 
the  discharge  of  the  same  w'eir  when  submerged.  These  coefficients 
will  give  approximate  results  at  best  and  can  not  be  relied  upon 
for  a  high  degree  of  accuracy  in  any  case.  To  obtain  the  discharge 
of  a  submerged  weir  by  means  of  these  coefficients,  first  the  discharge 
of  the  same  weir,  free,  should  be  taken  from  Table  i  or  2  for  the 
head  on  the  upstream  side  of  the  weir  and  this  discharge  then 
multiplied  by  the  proper  coefficient  obtained  from  Table  4. 

Illustration:  Suppose  it  is  desired  to  find  the  discharge  over  a 
submerged  standard  Cippoletti  weir  with  a  crest  length  of  3  feet 
when  the  head  on  the  upstream  side  is  found  to  be  1.32  feet  and  the 
head  on  the  downstream  side  of  the  weir  0.33  foot.  By  Table  2 
the  discharge  of  the  same  weir,  free,  under  the  same  head,  is  15.71 
second-feet.  The  ratio  d -i- H  =  0.33  -h  1.32  =  0.25,  for  which 
Table  4  gives  a  coefficient  of  0.958.  The  product,  15.71  X  0.958  = 
15.5  second -feet,  the  discharge  of  the  weir,  submerged. 


12  MEASUREMENT    OF   IRRIGATION    WATER. 

• 

22.  Tabic  5. — Table  5  contains  the  acre-foot  equivalents  of  given 
second-foot  discharges  for  stated  lengths  of  time.  This  table  is 
designed  to  assist  in  reducing  weir  discharges  to  acre-foot  quantities 
in  working  up  the  field  records  for  oflice  use.  By  means  of  this 
table  the  acre-foot  equivalent  of  any  second-foot  discharge  far  any 
length  of  time  may  be  obtained.  For  values  not  given  directly  in 
the  table  it  is  nccessarj-  only  to  multiply  by  the  proper  factors 
and  add. 

Illustration:  Suppose  it  is  desired  to  ascertiiin  how  many  acre- 
feet  are  represented  by  a  discharge  of  14.52  second-feet  flowing  for 
2  hours  and  15  minutes.  From  the  table  (remembering  that  the 
tabular  values  are  multiplied  by  10  or  by  100  by  moving  the 
decimal  point  one  or  two  places  to  the  right,  respectively): 

Acre-feer 

14        second-feet  flowing  2  hours  equals 2.  314 

14        second-feet  flowing  15  minutes  equals '.     .  289 

o.  52  second-feet  flowing  2  hours  equals c86 

o.  52  second-feet  flowing  15  minutes  equals on 

14.  52  second-feet  flowing  2  hours  and  15  minutes  eqfuals.  ...     2.  700 

PART   II.     SUBKEROED   ORIFICES. 

23.  Use  of  submerged  orifices  v.  weirs. — Where  there  is  sufficient 
fall  to  permit  of  the  measurement  of  water  by  means  of  a  weir  of 
reasonable  length,  the  weir  should  by  all  means  be  chosen  as  the 
most  desirable  measuring  device,  as  it  will  be  free  from  detrimental 
effects  from  weeds  and  trash.  Where,  however,  the  amount  of  fall 
available  for  measuring  the  water  is  not  adequate  for  the  use  of  a 
weir  of  reasonable  length,  the  submerged  orifice  should  be  used. 
In  the  measurement  of  water  in  laterals  and  farm  ditches  a  weir 
can  generally  be  used  for  all  cases  where  there  is  as  much  as  0.5  of 
a  foot  of  fall  available,  and  even  under  the  most  adverse  conditions 
the  weir  can  be  used  for  all  falls  exceeding  one  foot. 

24.  Definition  and  classification  of  orifices. — An  orifice  may  be 
defined  as  an  opening  so  placed  in  a  wall  of  a  channel  or  vessel 
carrying  or  holding  water  that  the  opening  lies  completely  below 
the  surface  of  the  water  on  the  upstream  side  thereof.  The  wall 
may  have  any  angular  position  from  horizontal  to  vertical,  the 
opening  may  have  any  geometrical  shape,  the  water  may  discharge 
into  air  or  into  water,  and  the  issuing  stream  may  or  may  not  be 
contracted.  The  orifices  generally  employed  for  the  measurement 
of  irrigation  water  are  either  circular  or  rcctangtilar  and  are  vertical, 
that  is,  are  placed  in  a  vertical  wall  in  a  canying  channel.  In  the 
early  days  of  irrigation  such  an  orifice  usually  discharged  into  air, 
in  which  case  the  orifice  was  said  to  be  free.  Since  the  more  general 
adoption  of  the  weir  for  measuring  irrigation  water  the  free  orifice 


SUBMERGED    ORIFICES.  1 3 

has  been  practically  abandoned  because  it  requires  considerable 
fall  for  its  use  and,  when  this  fall  is  available,  the  weir  is  more 
applicable.  Later  practice  has  developed  the  use  of  an  orifice  that 
discharges  into  water;  such  an  orifice  is  said  to  be  submerged.  The 
submerged  orifice  is  used  where  there  is  insufficient  fall  for  the  use 
of  a  weir.  In  addition  to  the  subdivision  of  vertical  orifices  into 
free  and  submerged  orifices,  either  of  these  classes  may  be  con- 
tracted or  suppressed.  A  contracted  orifice  is  one  with  its  perimeter 
so  far  removed  from  the  bounding  surfaces  of  the  water  prism  in  the 
channel  of  approach  or  other  surfaces  of  a  disturbing  nature  that 
the  filaments  of  water  are  fully  contracted  as  they  pass  through 
the  orifice .  A  suppressed  orifice  is  one  with  its  perimeter  coincident 
with  the  sides  of  the  channel  of  approach  or  with  other  sui  faces 
eliminating  contraction.  Evidently  an  orifice  may  be  contracted 
or  suppressed  on  any  part  or  all  of  its  perimeter  or  it  may  be  imper- 
fectly contracted  and  suppressed  on  any  part  or  all  of  its  perimeter. 
This  latter  condition  is  the  result  of  the  existence  of  a  disturbing 
surface  intervening  between  that  prodticing  contraction  and  that 
producing  suppression.  If  the  opening  is  not  sharp-edged  or  if  the 
wall  in  which  it  is  cut  or  formed  has  material  thickness  or  if  a  dis- 
charge tube  is  attached,  then  the  opening  becomes  a  submerged 
tube.  This  condition  may  exist  all  arovmd  the  opening  or  only 
partially  so,  or  it  may  be  caused  b}^  placing  too  close  to  the  opening 
the  bounding  surfaces  of  the  water  prism  in  the  channel  of  approach. 
For  these  different  conditions  different  coefficients  of  discharge 
apply.  ^  y  ;,  _ 

25.  Type  of  orifice  adopted. — The  principal  type  of  orifice  adopted 
by  the  service  for  the  measurement  of  irrigation  water  is  the  vertical, 
sharp-edged,  contracted,  rectangular,  submerged,  orifice.  This 
type  will  be  hereafter  designated  as  the  standard  submerged  rec- 
tangular orifice.  The  reasons  for  selecting  this  type  for  general  use 
are  that  it  is  well  suited  for  securing  accuracy  and  is  the  principal 
type  f.Dr  which  the  discharge  coefficient  has  been  carefully  deter- 
mined. 

26.  Definition  and  coiidilions  for  accuracy  of  standard  submerged 
rectangular  orifices. — The  standard  submerged  rectangular  orifice  is 
a  submerged  rectangular  orifice  with  its  four  sides  consisting  of  thin- 
edged  plates,  each  so  far  removed  from  the  adjacent  side,  bottom,  or 
top  of  the  water  prism  in  the  leading  channel  as  to  cause  the  fila- 
ments of  water  to  be  fully  deflected  from  their  normal  course  as 
they  pass  through  the  orifice.  The  deflection  is  approximately 
the  maximum  deflection  that  would  obtain  with  the  sides  of  the 
orifice  at  unlimited  distances  from  the  water  prism  boundaries. 
The  sides  of  the  orifice  may  be  made  of  planks  if  the  upstream  edges 
are  deiinite,  rectangular  comers,  but  it  is  best  to  use  a  thin  metal 
plate.  The  conditions  that  are  considered  necessary  to  secure  per- 
fect contraction  and  accuracy  of  measurement  are  as  follows: 


14  MEASUREMENT    OF    IRRIGATION    WATER. 

(a)  The  upstream  edges  of  the  orifice  should  be  sharp  and  smooth 
and  the  distance  of  each  from  the  bounding  surfaces  of  the  channel, 
both  on  the  upstream  and  on  the  dowiistream  side,  should  preferably 
be  not  less  than  twice  the  least  dimension  of  the  orifice. 

(6)  The  UDStream  face  of  the  orifice  wall  should  be  vertical. 

(c)  The  top  and  bottom  edges  should  be  level  from  end  to  end. 

(d)  Tlie  sides  should  be  truly  vertical. 

(e)  The  head  on  the  orifice  that  should  be  measured  is  the  actual 
difference  in  elevation  between  the  water  surface  on  the  upstream 
side  of  the  orifice  and  the  water  surface  on  the  downstream  side 

thereof.  .        .  r    i. 

(/)  The  cross-sectional  area  of  the  water  prism  for  20  to  30  feet 
from  the  orifice  on  the  upstream  and  on  the  downstream  side  thereof 
should  be  at  least  six  times  the  cross-sectional  area  of  the  orifice. 

(g)  Correction  should  be  made  for  velocity  of  approach  where 
appreciable  errors  are  caused  by  neglecting  the  head  due  to  it. 

27.  Suitable  dimensions  for  standard  submerged  rectangular  orifices.— 
The  most  suitable  dimensions  for  standard  submerged  rectangular 
orifices  are  those  in  which  the  height  is  considerably  less  than  the 
length.  This  is  due  to  the  fact  that  the  ratio  of  depth  to  width  of 
irrigation  canals  and  laterals  is  small.  Convenient  dimensions  for 
submerged  orifices  are  }4  foot  by  i  foot,  2  feet,  or  3  feet;  }4  foot  by  i 
foot,  lii  feet,  2  feet,  2^  feet,  or  3  feet;  %  foot  by  j}4  feet,  iK.ieet, 
2  feet,  2}i  feet,  or  2%  feet.  These  dimensions  will  give  orifices 
varying  in" area  from  0.25  to  2.0  square  feet  in  intervals  of  0.25  square 
foot.  Where  possible  an  orifice  of  i  square  foot  area  should  be  chosen, 
as  the  unit  area  simplifies  the  discharge  determination  somewhat  and 
will  give  discharges  ranging  from  0.0  to  nearly  3.5  second-feet  under 
heads  varying  from  0.0  to  0.5  foot.  However,  the  size  of  the  orifice 
selected  will  necessarily  be  determined  by  the  quantity  of  water  to 
be  measured  and  the  available  fall  that  can  be  utilized  therefor. 

28.  Formulas  for  standard  submerged  rectangular  orifice. — The  for- 
mula for  computing  the  discharge  of  the  standard  submerged  rec- 
tangular orifice,  without  velocity  of  approach,  is- as  follows: 

{13)     e=o.6iV^  A; 

and  with  velocity  of  approach  is  as  follows: 

(14)    Q'=o.6i  V29  (H+h)  A; 

in  which  O  is  the  discharge  in  second-feet  without  velocity  of  ap- 
proach; Cthe  discharge  in  second-feet  with  velocity  of  approach; 
g  gravity' in  feet;  H  the  measured  head  on  the  orifice  in  feet,  being 
equal  to  the  difference  in  elevation  of  the  water  surface  on  the  up- 
stream side  of  the  orifice  and  the  water  surface  on  the  downstream 
side  thereof;  h  the  head  due  to  velocity  of  approach  in  feet,  and  A 
the  area  of  the  orifice  in  square  feet. 


SUBMERGED   ORIFICES.  1 5 

29.  Velociiv  of  approach  in  submerged  orifice  meastirements . — So  far 
as  practicable  submerged  orifices  should  be  so  installed  as  to  make 
the  velocity  of  approach  negligible,  but  where  this  is  impracticable 
appropriate  corrections  therefor  should  be  made.  Attention  is 
called  to  the  fact  that  neglecting  moderate  velocities  of  approach 
with  low  heads  on  the  orifice  produces  relatively  large  errors,  whereas 
neglecting  comparatively  high  velocities  of  approach  with  large 
heads  on  the  orifice  produces  relatively  small  errors.  The  velocity 
of  approach  may  be  computed  from  formula  (7),  page  S,  and  after  the 
velocity  of  approach  is  determined,  the  head  due  to  the  velocity  of 
approach  may  be  computed  from  formula  (8),  page  8.  This  velocity 
head,  designated  as  h,  should  be  added  to  the  measured  head,  as 
indicated  by  formula  (14),  before  computing  the  discharge  by  the 
formula  or  before  taking  it  from  the  discharge  table. 

30.  Correction  for  suppression  of  coniraciion  in  submerged  orifica. — 
While  it  is  deemed  desirable  to  use  the  standard  submerged  rec- 
tangular orifice  so  far  as  conditions  will  permit,  it  may  be  necessary 
in  some  cases,  for  the  purpose  of  avoiding  accumulations  of  silt  on 
the  upstream  side  of  the  orifice,  to  suppress  bottom  contraction  by 
placing  the  lower  side  of  the  orifice  at  canal  grade,  and  cases  may 
now^  and  then  arise  i\"here  it  will  be  necessar\'  to  determine  the  dis- 
charge of  submerged  orifices  that  have  also  their  side  contractions 
suppressed.  The  discharge  coefl'.cients  where  suppression  exists  are 
not  well  determined,  and  it  is  therefore  undesirable  to  permit  sup- 
pression except  where  unavoidable.  In  such  cases  the  discharge  for 
the  submerged  rectangular  orifice  without  velocity  of  approach  may 
be  computed  approximately  by  the  following  formula: 

(15)     2i=o-6i  (i-f  0.15  r)  V29//  A; 
and  w  ith'velocity  of  approach  by  the  following  formula: 

(16)     Q\=o.6i  (i-fo.i5  r)  V29  {H-^K)  A; 

in  which  Qx  is  the  discharge  in  second-feet  of  the  suppressed  orifice 
without  velocity  of  approach;  0\  the  discharge  in  second-feet  of  the 
suppressed  orifice  with  velocity  of  approach;  r  the  ratio  of  the  sup- 
pressed portion  of  the  perimeter  of  the  orifice  to  the  whole  perimeter, 
and  H,  A,  and  h  have  the  same  significance  as  in  formulas  (13 )  and 
(14).  By  comparison  of  formula  (15^  to  formula  (13)  and  formula 
(16)  to  formula  (14)  the  following  relations  are  derived: 

(^7)     §-=§J'  =  i+o.i5  r=C; 

in  whichTc',?C?^3  Qi,  Q\,  and  r  have  the  same  significance  as  in  for- 
mulas (13)  to  (16)  and  Cis  aconstant  equal  to  i-f  0.15  r.  Itis  obvious 
that  C  applied  as  a  coefilcient  to  Q  or  O'  will  give  0^  or  Q\,  respec- 
tively. 


l6  MEASUREMENT   OF    IRRIGATION   WATER. 

31.  Construction  of  submerged  orifices. — Submerged  orifice  boxes 
should  be  substantially  constructed  of  lumber  or  concrete.  The 
orifice  box  should  be  of  sufficient  length  to  extend  downstream 
from  the  orifice  wall  far  enough  to  still  the  w^ater  before  it  passes 
back  into  the  earth  channel  below.  The  floor  should  be  depressed 
below  the  canal  grade  to  form  a  stilling  pool  and  the  floor  and  sides 
should  be  set  at  distances  from  the  orifice  opening  of  not  less  than 
twice  the  least  dimension  of  the  orifice.  A  flashboard  may  be  placed 
at  the  lower  end  of  the  orifice  box  to  secure  submergence  of  the 
orifice,  but  the  box  must  have  sufficient  length  in  such  a  case  to 
prevent  disturbance  in  the  water  issuing  from  the  orifice.  The 
orifice  wall  should  be  set  truly  vertical  and  should  reach  only  to  the 
maximum  water  level  so  as  to  form  an  overflow  in  case  of  trouble. 
Wing- walls  or  cut-off  walls  should  be  provided,  both  at  the  upper 
end  and  the  lower  end  of  the  orifice  box,  for  the  purpose  of  preventing 
erosion  of  the  canal  banks  and  leakage  on  water  around  the  structure. 

32.  Installation  of  submerged  orifices. — The  orifice  box  should  be 
installed  sufficiently  far  from  the"  turnout  to  permit  the  construc- 
tion of  a  pool  of  the  required  length  for  stilling  the  water  before 
it  passes  through  the  orifice.  The  pool  should  be  made  with  uni- 
form dimensions  and  with  its  bottom  about  one  foot  below^  the 
normal  grade  of  the  canal  to  insure  bottom  contraction.  The  struc- 
ture should  be  carefully  levelled  when  installed  and  thoroughly 
puddled  to  prevent  leakage.  A  gage  should  be  placed  on  the 
upstream  side  of  the  orifice  and  another  on  the  downstream  side 
thereof  having  the  same  zero  elevation.  The  upstream  gage  should 
be  located  at  a  convenient  place  on  the  upstream  side  of  the  orifice 
wall  and  the  downstream  gage  should  be  placed  on  the  side-wall  of 
the  orifice  box  sufficiently  far  downstream  from  the  orifice  wall  to 
register  the  true  back  pressure  on  the  orifice.  This  distance  will  be 
at  least  two  feet  for  small  orifices.  Great  care  should  be  taken  to  fix 
the  gages  truly  vertical  and  to  set  their  zero  marks  at  the  same 
elevation. 

33.  Care  of  submerged  orifices. — The  submerged  orifice  and  pool 
should  be  freed  from  weeds  and  trash  at  each  round  of  the  canal 
rider  and  the  pool  should  be  cleared  of  silt  often  enough  to  maintain 
proper  stilling  of  the  water  and  bottom  contraction  of  the  orifice. 
The  orifice  should  be  carefully  checked  from  time  to  time  to  insure 
that  the  dimensions  and  elevation  are  unchanged,  the  sides  truly 
vertical,  the  upper  and  lower  crests  level  and  the  zero  marks  of  the 
gages  at  the  same  elevation.  Inspection  should  be  made  from  time 
to  time  to  determine  whether  there  is  any  leakage  around  the  struc- 
ture and,  in  event  of  such  leakage,  the  structure  should  be  immedi- 
ately repuddlcd  and  the  orifice  should  again  be  checked  as  above 
indicated. 


CURRENT  METER  MEASUREMENTS.         IJ 

34.  Table  6. — Table  6  contains  discharges  in  second-feet  of  standard 
submerged  rectangular  orifices  without  velocity  of  approach  for  com- 
monly used  heads  and  orifice  areas,  computed  from  formula  (13),  page 
14.  The  method  of  using  the  table  is  apparent.  The  head,  H,  is 
the  observed  head  plus  the  head  due  to  any  velocity  of  approach 
that  may  exist. 

35.  Table  7.— Table  7  gives  coefficients,  which  applied  to  a  dis- 
charge given  by  Table  6  will  give  the  discharge  of  the  same  orifice 
suppressed  on  the  bottom  alone  or  on  the  bottom  and  two  sides.  For 
an  orifice  constructed  as  a  suppressed  orifice  or  one  in  which  silt  has 
collected  sufficiently  to  effect  suppression,  the  discharge  should  be 
corrected  by  means  of  this  table.  First  the  discharge  without  sup- 
pression should  be  taken  from  Table  6  and  then  multiplied  by  the 
proper  coefficient  taken  from  Table  7. 

Illustration :  Suppose  it  is  desired  to  find  the  discharge  of  a  standard 
submerged  rectangular  orifice  0.5  by  2.5  feet  with  bottom  and  side 
suppressions  under  a  head  of  0.18  foot.  For  an  area  of  1.25  square 
feet  (=0.5X2.5)  and  a  head  of  0.18  foot.  Table  6  gives  a  discharge  of 
2.593  second-feet.  For  a  height,  d,  of  0.5  foot  and  a  length,  /,  of  2.5 
feet,  with  bottom  and  sides  suppressed.  Table  7  gives  a  coefficient  of 
1.09.     Then  2.593Xi-09==2.826  second-feet,  the   discharge  desired. 

PART  III.   CURRENT   METER   GAGING   STATIONS. 

36.  Use  of  current  meter  stations  v.  weirs  and  submerged  orifices. — • 
Where  the  quantity  of  water  to  be  measured  is  large  and  the  available 
fall  small,  or  where  the  quantity  of  water  is  small  and  extremely 
heavily  laden  with  silt,  the  use  of  current  meter  stations  is  advis- 
able. Their  use  should  be  reduced  to  the  minimum,  however,  as 
their  operation  is  comparatively  expensive  and  the  results  are 
relatively  unsatisfactory.  Only  a  very  brief  discussion  of  current 
meter  stations  will  be  given  here  and  the  reader  is  referred  to  the 
Water-Supply  Papers  of  the  United  States  Geological  Survey  and 
technical  books  on  the  subject  for  further  information. 

37.  Selection  of  current  meter  stations. — A  current  meter  station 
should  be  located  in  a  straight  uniform  stretch  of  canal  with  smooth 
banks  and  bed  of  permanent  nature,  so  far  removed  from  turnouts, 
drops,  and  checks  that  the  relation  of  discharge  to  gage  height  will 
not  be  disturbed  by  these.  In  many  canals  these  conditions  are 
difficult  to  find  in  combination  and  unusual  care  has  to  be  taken  to 
obtain  a  station  that  will  give  good  results. 

38.  Current  meter  station  equipment. — The  essential  features  of  a 
current  meter  station  are  a  gage,  a  bench  mark,  fixed  measuring 
points  in  the  channel  cross  section,  and  a  stayline  to  hold  the  meter 
in  the  measuring  plane  or  cross  section  when  the  velocity  is  high 

57737—18 3 


1 8  MEASUREMENT   OF   IRRIGATION   WATER. 

and  the  water  deep.  Tlie  gage  should  be  of  a  good  design,  sub- 
stantially installed  where  it  will  indicate  the  water  elevation  at  all 
stages,  and  should  be  so  graduated  as  to  permit  accurate  readings  to 
hundredths  of  a  foot.  (See  fig.  2.)  The  bench  mark  should  be 
conveniently  and  permanently  located  and  the  elevation  of  the 
datum  of  the  gage  should  be  carefully  referred  to  it.  The  measuring 
points  should  be  located  in  a  cross  section  at  right  angles  to  the 
stream  flow  on  a  tagged  wire  stretched  across  the  channel  or  on  a 
bridge  located  at  the  station.  Where  the  canal  is  shallow  enough 
to  permit  of  wading  measurements,  the  tagged  wire  will  be  appli- 
cable; otherwise  a  highway  bridge  or  a  small  bridge  constructed 
for  the  purpose  should  be  used.  The  measuring  points  should  be 
permanently  fixed  and  marked  at  equal  intervals  of  from  two  to  ten 
feet  depending  upon  the  size  of  the  canal.  The  stayline  should  be 
stretched  across  the  canal  far  enough  above  the  measuring  section 
to  hold  the  current  meter  in  proper  position.     (See  fig.  i.) 

39.  Ctirrent  meters. — The  essential  features  of  all  current  meters 
are  a  wheel  capable  of  rotation  by  impact  of  water  and  a  device  for 
determining  the  number  of  revolutions  of  the  wheel.  The  relation 
of  the  velocity  of  the  water  to  the  angular  velocity  of  the  wheel  or 
the  number  of  revolutions  of  the  wheel  in  a  given  time  is  deter- 
mined by  experiment,  and  should  be  checked  and  redetermined 
from  time  to  time.  A  sample  rating  table  for  4  small  Price  meter 
is  given  in  Table  8.  The  two  types  of  meters  most  widely  used  are 
the  Haskell  and  the  Price.  The  wheel  of  the  former  consists  of  a 
screw-shaped  head  mounted  on  a  horizontal  axis,  while  that  of  the 
latter  consists  of  a  group  of  conical  cups  set  with  the  axes  of  the 
cones  tangent  to  a  circle,  the  whole  group  being  mounted  on  a  ver- 
tical axis.  Both  types  are  provided  with  vanes  to  keep  the  wheel 
headed  against  the  current,  weights  for  sinking  the  meter,  a  cable 
for  handling  the  meter,  and  electric  or  acoustic  sounder  for  indicating 
the  number  of  revolutions  and  connections  from  the  meters  to  the 
sounding  devices.  The  Price  meter  has  been  developed  by  the 
United  States  Geological  Survey  for  use  in  its  work  and  a  cut  of  it 
as  now  manufactured  is  shown  in  figure  4. 

40.  Methods  of  measurement. — Soundings,  either  with  a  meter  or 
with  a  special  sounding  line  and  weight,  should  be  made  at  the  per- 
manent measuring  points.  The  mean  velocity  at  each  of  these 
measuring  points  should  then  be  determined  by  means  of  the  cur- 
rent meter,  in  accordance  with  one  of  the  approved  methods  of 
determining  mean  velocities. 

41.  Methods  of  determining  mean  velocities. — There  are  five  general 
methods  of  determining  mean  velocities  in  a  vertical  line  with  a 
current  meter:  (a)  By  taking  the  velocity  at  0.2  and  that  at  0.8  of 
the  water  depth  and  obtaining  one-half  the  sum;  (i)  by  taking  the 
velocity  at  0.6  of  the  water  depth;  (c)  by  taking  the  velocities  at 


CURRENT  METER  MEASUREMENTS.         1 9 

equal  vertical  intervals  of  0.5  of  a  foot  or  more  and  obtaining  their 
arithmetical  mean,  or  finding  the  mean  value  from  a  curve  derived 
by  plotting  the  measurements  on  cross  section  paper;  {d)  by  taking 
the  velocity  near  the  water  surface  and  using  from  0.85  to  0.95  of 
the  result,  depending  on  the  depth  of  water,  its  velocity,  and  the 
nature  of  the  canal  Ised,  and  (e)  by  taking  velocity  in  the  vertical 
line  by  slowly  and  imiformly  lowering  and  raising  the  meter  through- 
out the  range  of  water  depth  one  or  more  times.  Of  the  methods 
given,  the  first  two  are  most  used  in  canal  work. 

42.  Methods  of  compzituig  discharge  tneasurements . — There  are  two 
important  methods  of  computing  discharges  from  measurements 
made  by  current  meters.  Both  of  these  methods  are  based  on 
determining  tlie  discharges  of  the  elementary  areas  between  the 
measiu-ing  points  and  taking  their  sum.  In  one  of  the  methods  the 
discharge  is  computed  separately  for  each  elementary  area  on  the 
assumption  that  both  the  velocity  and  the  water  depth  vary  uni- 
formly from  one  measuring  point  to  another.  This  may  well  be 
termed  the  "straight-line"  method,  and  the  formula  for  computing 
the  discharge  of  the  elementary'  area  is  as  follows: 


(,S),.(I^')("-f»), 


in  which  a  and  b  are  the  water  depths  in  feet  at  two  adjacent 
measuring  points,  Va  and  Vb  the  respective  mean  velocities  in 
feet  per  second  at  these  points,  I  the  distance  in  feet  between  the 
points,  and  q  the  discharge  in  second-feet  for  the  elementary  area. 
Formula  (18)  is  well  suited  to  computing  discharges  in  canals  con- 
forming in  cross  section  to  their  original  trapezoidal  or  rectangular 
dimensions.  In  the  other  method  the  discharge  is  computed  for 
consecutive  pairs  of  elementary  areas  on  the  assumption  that  the 
velocities  and  the  water  depths  for  three  consecutive  measuring 
points  each  lie  on  the  arc  of  a  parabola.  This  method  might  well  be 
termed  the  parabolic  method  and  the  formula  for  computing  the 
discharge  for  each  pair  of  elementar}''  areas  is  as  follows: 

in  which  a,  b,  and  c  are  the  water  depths  in  feet  at  three  consecutive 
measuring  points,  Va,  Vb,  and  Vc  the  respective  mean  velocities 
in  feet  per  second  at  these  points,  /  the  distance  in  feet  between  the 
consecutive  points,  and  q^  the  discharge  in  second-feet  for  the  pair 
of  elementary  areas.  Formula  (19)  is  more  particularly  applicable 
to  river  channels  and  old  canals  that  have  cross  sections  conforming 
in  a  general  way  to  the  arc  of  a  parabola  or  to  a  series  of  arcs  of  dif- 
ferent parabolas.     (See  Table  9.) 


20  MEASUREMENT   OF   IRRIGATION   WATER. 

43.  Range  of  discharge  measurements. — ^The  discharge  measure- 
ments of  a  canal  at  a  current  meter  station  should  be  taken  at  suffi- 
cient intervals  of  gage  heights  to  permit  of  making  accurate  velocity, 
area,  and  discharge  curves.  Inasmuch  as  water  is  usually  turned  into 
the  canals  gradually  in  the  beginning  of  each  irrigation  season,  it 
is  possible  at  this  time  to  get  well-distributed  measurements  for  tlie 
condition  of  the  canal  at  this  season .  The  canal  bed  at  a  well- 
selected  current  meter  station  is  generally  permanent  in  character, 
and  a  permanent  rating  curve  for  the  canal  could  be  made  were  it 
not  for  the  fact  that  increased  vegetable  growth  in  the  canal  and  on 
its  banks  during  the  irrigation  season,  together  with  accumulations 
of  silt,  decrease  the  discharge  capacity-  for  all  gage  heights  during 
the  latter  part  of  the  irrigation  season.  This  fact  must  be  taken 
into  consideration  in  computing  the  quantity  of  water  carried  by  a 
canal  during  the  irrigation  season.  If  the  canal  is  cleaned  diiring 
the  season,  the  relation  of  discharge  to  gage  height  is  again  dis- 
turbed. These  changing  relations  of  discharge  to  gage  height  are 
the  chief  source  of  errors  and  difficulties  in  irrigation  canal 
hydrography. 

44.  Daily  gage  heights. — In  order  to  determine  the  quantity  of 
water  carried  by  a  canal  at  a  current  meter  station  it  is  necessary 
to  read  the  gage  twice  daily  and  additionally  at  such  times  as 
changes  of  stage  are  made  in  the  canal.  These  readings  should  be 
taken  by  the  canal  riders  while  on  their  daily  rounds.  The  gages 
should  be  read  accurately,  generally  to  the  nearest  hundredth  of 
a  foot.  The  gage  should  be  read  carefully  also  b^-  the  hydrographer 
both  before  and  after  taking  a  current  meter  measurement. 

45.  Computation  of  discharges. — The  current  meter  measurements 
at  a  station  are  interpreted  and  extended  to  cover  all  gage  heights 
at  the  station  by  means  of  curves  drawn  on  cross-section  paper. 
To  construct  these  curves  the  discharges  of  the  canal  in  second-feet 
as  computed  from  individual  current  meter  discharge  measurements, 
the  corresponding  mean  velocities  in  feet  per  second  and  the  cross 
sectional  areas  in  square  feet  for  each  measurement  are  plotted  as 
abscissas,  each  to  a  convenient  scale,  with  the  common  gage  heights 
as  ordinates.  The  most  probable  area  curve  is  drawn  through  the 
area  plottings  and  from  this  the  accuracy  of  the  area  computations 
and  of  the  soundings  are  checked  and,  in  case  of  a  shifting  channel, 
changes  in  the  rating  section  are  discovered.  The  most  probable 
velocity  curve  is  drawn  through  the  velocity  plottings  on  the  sheet 
to  provide  a  graphic  means  of  finrling  inaccuracies  in  the  computa- 
tions and  noting  disturbances  in  the  velocity  due  to  obstructions  in 
the  channel  or  changes  in  the  velocity  due  to  increased  roughness 
of  the  channel  from  vegetable  growths  in  the  canal.  The  discharge 
curve  is  then  drawn  through  the  discharge  points  on  the  cross-section 


CURRENT  METER  MEASUREMENTS.  21 

paper,  giving  due  weight  to  the  various  measurements  and  to  prod- 
ucts of  the  mean  velocity  and  area  abscissas  for  various  gage  heights 
throughout  the  range  of  canal  depths.  WTiere  the  conditions  of 
flow  of  the  canal  have  not  been  changed  during  the  irrigation  season, 
it  will  generally  be  comparatively  easy  to  draw  a  satisfactory  curve. 
WTiere,  however,  the  relation  of  discharge  to  gage  height  has  been 
afTected  by  vegetable  growth,  or  the  introduction  of  other  obstruc- 
tions, these  conditions  must  be  given  careful  consideration  and 
another  curve  dra-'.vn  for  that  part  of  the  irrigation  season  during 
which  such  conditions  have  existed.  The  discharge  curve  for  these 
conditions  will  generally  be  parallel  to  the  discharge  curve  for  the 
earlier  part  of  the  irrigation  season  when  the  canal  is  clean.  For 
the  period  during  which  the  change  is  in  progress  the  discharges 
must  be  estimated  on  the  theory-  of  proportion  from  the  two  ciu-ves 
constructed  for  the  extreme  conditions.     (See  fig.  3.) 

46.  Rating  table. — From  the  rating  curve  the  rating  table  may 
be  prepared  for  each  tenth  or  hundredth  of  a  foot  of  gage  height  a^s 
the  condition  of  accuracy  may  require,  ranging  from  zero  to  the  ma:^:i- 
mum  height  of  water  in  the  canal.  In  case  of  canals  affected  by 
vegetable  growth  two  such  rating  tables  will  have  to  made,  one 
applying  to  the  early  part  of  the  irrigation  season  when  the  canal  is 
clean  and  the  other  to  the  latter  part  of  the  irrigation  season  when 
the  canal  is  in  bad  condition.  Daily  discharges  will  also  have  to  be 
estimated  for  the  period  in  which  the  change  in  the  canal  is  being 
effected.  In  case  the  canal  is  cleaned  at  any  time  during  the  irriga- 
tion season,  this  fact  must  be  given  consideration  in  preparing  the 
necessary  additional  rating  curves.     (See  Table  10.) 

47.  Compilation  of  daily  and  montlily  discharges. — By  means  of 
daily  gage  heights  and  the  rating  tables  the  daily  discharges  may 
readily  be  compiled,  and  adding  these  gives  the  monthly  discharges 
and  the  total  amount  of  water  carried  by  the  canal  during  the 
irrigation  season. 


I 


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MEASUREMENT   OF   IRRIGATION   WATER. 


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MEASUREMENT   OF   IRRIGATION   WATER. 


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Fig.  2. — Steward  water  gages. 


24 


MEASUREMENT   OF   IRRIGATION   WATER. 


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MEASUREMENT    OF   IRRIGATION   WATER. 


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57737—18 1 


26 


MEASUREMENT   OF   IRRIGATION   WATER. 


Table  1. — Discharge  of  standard  contracted  rectangular  weirs  in 
cubic  feet  per  second.  Values  below  and  to  left  of  heavy  line 
determined  experimentally;  others  computed  from  the  formula 

Q  =  3.33  (L  —  .2H)  Hi.     (Sec  paragraphs  8  and  18.) 


Length  of  weir  L,  feet. 

Head  H, 

,  feet 

j 

0.5 

1.0 

1.5      2.0 

3.0 

4.0 

5.0       6.0 

7.0 

8.0 

9.0 

0.01 

0.002 

0.003 

0.005 

0.007 

0.010 

0.013    0.016 

0.020 

0.023 

0.026 

0.030 

.02 

.005 

.009 

.014 

.019 

.028 

.037 

.047 

.056 

.066 

.075 

.085 

.03 

.009 

.017 

.026 

.034 

.052 

.069 

.086 

.104 

.121 

.138 

.1.55 

.04 

.013 

.026 

.040 

.053 

.079 

.106 

.133 

.159 

.186 

.213 

.239 

.05 

.018 

.037 

.055    .074 

.111 

.148 

.186 

.223 

.260 

.297 

.334 

.06 

.024 

.048 

.073 

.097 

.146 

.195 

.244 

.293 

.342 

.391 

.439 

.07 

.030 

.061 

.092 

.123 

.184 

.246 

.308 

.369 

.431 

.493 

.554 

.08 

.036 

.074 

.112 

.149 

.225 

.300 

.375 

.451 

.526 

.601 

.676 

.09 

.043 

.088 

.133 

.178 

.268 

.358 

.448 

.538 

.628 

.718 

.807 

.10 

.051 

.103 

.156 

.208 

.314 

.419 

.524 

.630 

.735 

.840 

.945 

.11 

.058 

.119 

.179 

.240 

.362 

.483 

.605 

.726 

.848 

.969 

1.091 

.12 

.066 

.135 

.204 

.273 

.412 

.550 

.689 

.827 

.965 

1.104 

1.242 

.13 

.074 

.152 

.230 

.308 

.464 

.620 

.776 

.933 

1.089 

1.245 

1.401 

.14 

.082 

.169 

.257 

.344 

.518 

.693 

.867 

1.041 

1.216 

1.390 

1.565 

.15 

.091 

.188 

.284 

.381 

.575 

.768 

.962 

1.155 

1.349 

1..542 

1.736 

.16 

.100 

.206 

.313 

.419 

.632 

.845 

1.059 

1.272 

1.485 

1.698 

1.911 

.17 

.109 

.225 

.342 

.459 

.692 

.926 

1.159 

1.392 

1.626 

1.859 

2.093 

.18 

.122 

.245 

.372 

.499 

.754 

1.008 

1.262 

1.517 

1.771 

2.025 

2.279 

.19 

.132 

.265 

.403 

.541 

.817 

1.093 

1.369 

1.644 

1.920 

2.196 

2.472 

.30 

.142 

.286    .435 

.,584 

.881 

1.179 

1.477 

1.775 

2.073 

2..370 

2.668 

.21 

.152 

.307 

.467 

.627 

.948 

1.269 

1.589 

1.910 

2.230 

2.551 

2.871 

.22 

.162 

.328 

.500 

.672 

1.016 

1.359 

1.703 

2.046 

2.390 

2.734 

3.077 

.23 

.173 

.350 

.534 

.718 

1.085 

1.452 

1.820 

2.187 

2.554 

2.921 

3.289 

.24 

.184 

.373 

.568 

.764 

1.156 

1.547 

1.939 

2.331 

2.722 

3.113 

3.505 

.25 

0.195 

.395 

.603 

.811 

1.228 

1.644 

2.060 

2.476 

2.893 

3.309 

3.725 

.26 

.419 

.639 

.860 

1.301 

1.743 

2.185 

2.626 

3.067 

3.509 

3.951 

.27 

.442 

.675 

.909 

1.376 

1.843 

2.311 

2.778 

3.245 

3.712 

4.179 

.28 

.466 

.712 

.9.59 

1.4.53 

1.946 

2.439 

2.933 

3.426 

3.919 

4.413 

.39 

.490 

.750 

1.010 

1.530 

2.050 

2.570 

3.090 

3.610 

4.130 

4.650 

.30 

.514 

.788 

1.061 

1.609 

2.156 

2.703 

3.251 

3.797 

4.344 

4.892 

.31 

.539 

.827 

1.114 

1.689 

2.263 

2.838 

3.413 

3.988 

4.563 

5.137 

.33 

.564 

.866 

1.167 

1.770 

2.373 

2.975 

3.578 

4.181 

4.784 

5.387 

.33 

.590 

.905 

1.221 

1.852 

2.4S3 

3.115 

3.746 

4.377 

5.009 

5.640 

.34 
.35 

.615 

.945 
.986 

1.275 
1.331 

1.936 
2.020 

2.596 
2.710 

3.256 
3.399 

3.916 
4.089 

4.577 
4.778 

5.237 
5.468 

5.897 

.658 

6.157 

.36 

.686 

1.027 

1.387 

2.106 

2.825 

3.545 

4.264 

4.983 

5.703 

6.422 

.37 

.714 

1.069 

1.443 

2.193 

2.943 

3.692 

4.441 

5.191 

5.941 

6.690 

.38 

.743 

1.111 

1.501 

2.281 

3.061 

3.841 

4.621 

5.401 

6.181 

6.961 

.39 

.772 

1.153 

1.559 

2.370 

3.181 

3.992 

4.803 

5.614 

6.425 

7.236 

.40 

.801 

1.196 

1.617 

2.460 

3.302 

4.145 

4.987 

5.829 

6.672 

7.514 

.41 

.830 

1.240 

1.677 

2. .551 

3.425 

4.299 

5.173 

6.048 

6.922 

7.796 

.42 

.860 

1.283 

1.737 

2.643 

3.549 

4.456 

5.362 

6.269 

7.175 

8.081 

.43 

.890 

1.328 

1.797 

2.736 

3.675 

4.614 

5.553 

6.492 

7.431 

8.370 

..44 

.920 

1.372 

1.858 

2.830 

3.802 

4.774 

5.746 

6.718 

7.690 

8.661 

.45 

.9.50 

1.417 

1.920 

2.925 

3.930 

4.935 

5.941 

6.946 

7.951 

8.956 

^4C 

.981 

1.463 

1.982 

3.021 

4.060 

5.099 

6.138 

7.177 

8.216 

9.255 

.47 

1.012 

l.,509 

2.045 

3.118 

4.191 

5.264 

6.337 

7.410 

S.483 

9.556 

.48 

1.044 

1.555 

2.108 

3.216 

4. .323    5.431 

6.538 

7.645 

8.753 

9.860 

.49 

1.077 

1.601 

2.172 

3.315 

4.457    5..599 

6.741 

7.8g3 

9.026 

10.168 

0.5O 

1.111 

1.648 

2.237 

3.414 

4.591    5.769 

6.946 

8.123 

9.301 

10.478 

MEASUREMENT   OF  IRRIGATION   WATER. 


27 


Table  1. — Discharge  of  standard  contracted  rectangular  weirs  in 
cubic  feet  per  second.  Values  below  and  to  left  of  heavy  line 
determined  experimetitally;  others  computed  from  the  formula 
Q  =  3.33  (L  —  .2H)  Hi  .     (See  paragraphs  8  and  18.) 


Head  B, 
feet 


Length  of  weir  L,  feet. 


1.5 


2.0 


3.0    {     4.0 


5.0  6.0 


7.0 


8.0 


9.0 


0.51 
.52 
.53 

.54 
.55 
.56 
.67 

.58 
.59 
.60 
.61 
.63 
.63 
.64 
.65 
.66 
.67 

.68 
.69 
.70 
.71 
.72 
.73 
.74 
.76 
.76 
.77 
.78 
.79 
.80 
.81 
.82 
.83 
.84 
.85 
.86 
.87 
.88 
.89 
.90 
.91 
.92 
.93 
.94 
.95 
.96 
.97 
.98 
.99 
1.00 


1.695 

2.302 

1.743 

2.367 

1.791 

2.434 

1.839 

2.500 

1.888 

2.567 

1.937 

2.635 

1.986 

2.703 

2.036 

2.771 

2.085 

2.840 

2.136 

2.909 

2.186 

2.979 

2.237 

3.050 

2.28S 

3.121 

2.339 

3.192 

2.391 

3.263 

2.443 

3.335 

2.495 

3.408 

2.547 

3.58 

2.599 

3.66 

2.652 

3.74 

2.705 

3.82 

2.759 

3.90 

2.813 

3.98 

2.866 

4.06 

2.920 

4.14 
4.22 

4.30 

4.38 

4.46 

4.54 

4.62 

4.70 

4.78 

4.87 

4.96 

5.05 

5.14 

5.23 

5.32 

5.41 

5.50 

5.59 

5.68 

..... 

5.77 

5.86 

5.95 

6.04 

6.13 

6.22 

' 

6.31 

3.515 
3.616 
3.719 
3.821 
3.925 
4.030 
4.136 
4.242 
4.349 
4.457 
4.566 
4.675 
4.786 
4.897 
5.00s 
6.121 
5.234 
5.348 
5.462 
5.578 
5.694 
5.810 
5.928 
6.046 
6.164 

6.283 
6.403 
6.524 
6.645 
6.767 
6.8S9 
7.013 
7.136 
7.260 
7.385 
7.511 
7.635 
7.763 
7.S90 
8.018 
8.146 
8.275 
8.404 
8.534 
8.664 
8.795 
8.927 
9.059 
9.191 
9.324 


4.727 

5.940 

7.153 

4.S65 

6.114 

7.362 

5.003 

6,288 

7.573 

5.143 

6.464 

7.786 

6.284 

6.642 

8.000 

5.426 

6.821 

8.217 

5..J69 

7.002 

8.435 

6.713 

7.184 

8.655 

5.858 

7.307 

8.877 

6.005 

7.552 

9.100 

6.152 

7.739 

9.325 

6.301 

7.927 

9.553 

6.451 

8.116 

9.781 

6.602 

8.307 

10.012 

6.753 

8.499 

10.244 

6.906 

8.692 

10.477 

7.060 

8.886 

10.712 

7.215 

9.083 

10.9,50 

7.371 

9.280 

11.188 

7.528 

9.478 

11.429 

7.686 

9.678 

11.670 

7.845 

9.879 

11.913 

8.005 

10.082 

12.1.59 

8.165 

10.285 

12.405 

S.327 

10.490 

12.653 

8.490 

10.696 

12.902 

8.653 

10.903 

13.153 

8.818 

11.112 

13.406 

8.983 

11.321 

13.660 

9.150 

11.533 

13.915 

9.317 

11.745 

14.172 

9.485 

11.958 

14.431 

9.C54 

12.172 

14.690 

9.824 

12.388 

14.951 

9.995 

12.604 

15.214 

10.106 

12.822 

15.478 

10.339 

13.041 

15.743 

10.512 

13.261 

16.010 

10.6S6 

13.482 

16.278 

10.861 

13.704 

16.547 

11.0.37 

13.927 

16.818 

11.213 

14.152 

17.090 

11.391 

14.377 

17.363 

11.509 

14.603 

17.638 

11.748 

14.S31 

17.915 

11.927 

15.060 

18.192 

12.10s 

1.5.289 

18.471 

12.289 

15.520 

18.7.50 

12.471 

15.751 

19.032 

12.654 

15.984 

19.314 

8.. 366 

8.611 

8.858 

9.107 

9.359 

9.612 

9.S6S 

10.126 

10.386 

10.647 

10.912 

11.178 

11.447 

11.717 

11.989 

12.263 

12.539 

12.817 
13.097 
13.379 
13.663 
13.948 
14.236 
14.525 
14.816 
15.109 
15.403 
15.700 
15.998 
16.298 
16.000 
16.903 
17.208 
17.515 
17.823 
18.134 
18.445 
18.759 
19.074 
19. .391 
19.709 
20.029 
20.350 
20.673 
20.998 
21.324 
21.652 
21.981 
22.312 
22.644 


9.579 

9.800 
10.143 
10.428 
10.717 
11.008 
11.301 
11.597 
11.895 
12.195 
12.498 
12.804 
13.112 
13.422 
13.734 
14.04S 
14.365 

14.684 
15.005 
1.5.329 
15.655 
15.982 
16.313 
16.645 
16.979 
17.315 
17.0.53 
17.094 
IS. 336 
IS.GSl 
19.027 
19.376 
19.726 
20.079 
20.433 
20.790 
21.147 
21.508 
21.809 
22.234 
22.599 
22.967 
23.337 
23.708 
24.081 
24.4.56 
24.833 
25.212 
25.592 
25.974 


10.791 

11.108 
11.428 
11.750 
12.075 
12.403 
12.734 
13.067 
13.404 
13.743 
14.085 
14.430 
14.777 
15.127 
15.479 
15.8,34 
16.191 

16.552 
16.914 
17.280 
17.647 
18.017 
18.390 
18.704 
19.142 
19.521 
19.903 
20.288 
20.074 
21.064 
21.455 
21.849 
22.244 
22.643 
23.043 
23.445 
23.8.50 
24.257 
24.665 
25.077 
25.490 
25.906 
26.323 
26.743 
27.165 
27.588 
28,015 
28.442 
28.872 
29.304 


28 


MEASUREMENT   OF   IRRIGATION   WATER. 


Table    1 — Discharge   of  standard   contracted    rectangular   weirs   in 
cubic  feet  per  second.     I'alues  to  left  of  heavy  line  determined 
experimentally;  others  computed  from  the  formula  Q  =  3.33 
(L  —  .2H)  Hi.     (Sec  paragraphs  8  and  18.) 


Length  of  weir 

L,  feet. 

Head  //. 

feet 

3.0 

4.0 

5.0 

6.0 

7.0 

8.0 

9.0 

1.01 

9.87 

12.838 

16.218 

19.598 

22.978 

26.358 

29.738 

1.03 

10.01 

13.022 

16.452 

19.883 

23.313 

26.743 

30.174 

1.03 

10.15 

13.207 

16.688 

20.169 

23.050 

27.131 

30.612 

1.04 

10.30 

13.394 

16.924 

20.4.56 

23.988 

27.. 520 

31.051 

1.05 

10.45 

13.579 

17.162 

20.714 

24.327 

27.910 

31.493 

l.OS 

10.60 

13.763 

17.401 

21.035 

24.669 

28.303 

31.937 

1.07 

10.75 

13.954 

17.640 

21.325 

25.011 

28,697 

32.383 

1.08 

10.90 

14.143 

17.880 

21.618 

25.3,55 

29.093 

32.830 

1.0!) 

11.05 

14.332 

18.121 

21.911 

25.700 

29.490 

33.279 

1.10 

11.20 

14.522 

18.364 

22.206 

26.047 

29.889 

33.731 

1.11 

11.35 

14.713 

18.607 

22..501 

26.. 395 

30.290 

34.184 

1.13 

11. ,50 

14.904 

18.851 

22.798 

26.745 

30.692 

34.639 

1.13 

11.65 

15.096 

19.096 

23.096 

27.096 

31.096 

35.096 

1.14 

11.80 

15.289 

19.342 

23.390 

27.448 

31.501 

35.555 

1.15 

11.95 

15.482 

19.589 

23.696 

27.. 802 

31,909 

36.016 

1.16 

12.10 

15.676 

19.8.37 

23.997 

28.157 

32.318 

36.478 

1.17 

12.25 
12.40 

15.871 
16.006 

20.085 
20.335 

24.. 300 
24.603 

28.513 

32.728 

36.943 

1.18 

28.871 

33.140 

37.408 

1.19 

12.55 

16.202 

20.585 

24.908 

29.231 

33.553 

37.876 

1.30 

12.70 

16.4.59 

20.836 

25.214 

29..591 

33.969 

38..346 

1.31 

12.85 

16.656 

21.088 

25.521 

29.953 

34.385 

38.817 

1.33 

13.00 

16.854 

21.341 

25.829 

30.316 

34.803 

39.291 

1.33 

13.15 

17.053 

21.595 

26.138 

30.681 

35.223 

39.700 

1.34 

13.31 

17.252 

21.850 

26.448 

31.046 

35.644 

40.243 

1.35 

13.47 

17.452 

22.105 

26.759 

31.413 

36.067 

40.721 

1.36 

13.63 

17.652 

22.362 

27.072 

31.782 

36.491 

41.201 

1.37 

13.79 

17.853 

22.619 

27.385 

32.151 

36.917 

41.683 

1.38 

13.95 

18.055 

22.877 

27.700 

32.522 

37.345 

42.167 

1.39 

14.11 

18.257 

23.136 

28.015 

32.894 

37.773 

42.652 

1.30 

14.27 

18.460 

23.396 

28.331 

33.267 

38.203 

43.139 

1.31 

14.43 

18.663 

23.656 

28.649 

33.642 

38.635 

43.628 

1.33 

14.. ^9 

18.867 

23.918 

28.968 

34.018 

39.068 

44.119 

1.33 

14.75 

19.072 

24.180 

29.287 

34.395 

39.503 

44.611 

1.34 

14.91 

19.277 

24.443 

29.608 

34.773 

39.939 

45.104 

1.35 

15.07 

10.483 

24.706 

29  929 

35.153 

40.376 

45.599 

1.36 

15.23 

19.689 

24.970 

so!  2.52 

35.533 

40.815 

46.096 

1.37 

15.39 

19.896 

25,236 

30.576 

35.915 

41.255 

46.595 

1.38 

15..55 

20.104 

25.502 

30.900 

36.299 

41.697 

47.096 

1.39 

15.71 

20.312 

25.769 

31.226 

36.083 

42,140 

47.598 

1.40 

15.87 

20.520 

26.036 

31.553 

37.069 

42,585 

48.101 

1.41 

16.03 

20.729 

26.305 

31.880 

37.455 

43.031 

48.606 

1.43 

16.19 

20.939 

26.574 

32.209 

37.843 

43.478 

49.113 

1.43 

16..35 

21.149 

26.843 

32.538 

38.2.32 

43.927 

49.621 

1.44 

16.51 

21.359 

27.114 

32.808 

38.622 

44.376 

50.131 

1.45 

16.68 

21.571 

27.385 

33.200 

39.014 

44.828 

50.643 

1.46 

16.85 

21.783 

27.657 

33.5.32 

39.406 

45.281 

51.155 

1.47 

17.02 

21.995 

27.930 

33.805 

39.800 

45.735 

51.670 

1.48 

17.19 

22.208 

28.204 

34.199 

40.195 

46.191 

52.187 

1.49 

17.36 

22.421 

28.478 

34.534 

40.. 59 1 

46.647 

52.704 

1.50 

17.53 

22.635 

28.753 

34.870 

40.988 

47.105 

53.223 

MEASUREMENT   OP  IRRIGATION   WATER. 


29 


Table   1 — Discharge   of  standard   contracted    rectangular  weirs   in 
)    cubic  feet  per  second,  computed  from  the  formula  Q  =  3.33 

{L  —  .2H)  Hi.     (See  paragraphs  8  and  18.) 


Length  of 

weir  L,  feet 

Head  H, 

feet 

4.0 

6.0 

6.0 

7.0 

8.0 

9.0 

1.51 

22.849 

29.028 

35.207 

41.386 

47.565 

53.744 

1.63 

23.065 

29.305 

35.545 

41.786 

48.026 

54.267 

1.53 

23.279 

29.581 

35.883 

42.185 

48.487 

54.780 

1.54 

23.495 

29.859 

36.223 

42.587 

48.951 

55.315 

1.55 

23.712 

30.138 

36.564 

42.990 

49.416 

55.842 

1.56 

23.929 

30.417 

36.905 

43.394 

49.882 

56.370 

1.57 

24.146 

30.697 

37.248 

43.799 

50.349 

56.900 

1.58 

24.364 

30.978 

37.591 

44.205 

50.818 

57.432 

1.59 

24.583 

31.259 

37.935 

44.612 

51.288 

57.965 

1.60 

24.801 

31.540 

38.280 

45.019 

51.7.59 

58.498 

1.61 

25.020 

31.823 

38.626 

45.428 

52.231 

59.034 

1.63 

25.240 

32.106 

38.973 

45.839 

52.705 

59.571 

1.63 

25.460 

32.390 

39.320 

46.250 

53.180 

60.110 

1.64 

25.681 

32.G75 

39.60a 

46.662 

53.650 

60.649 

1.65 

25.902 

32.960 

40.018 

47.075 

54.133 

61.191 

1.66 

26.124 

33.246 

40.308 

47.490 

54.612 

6 1.7.34 

1.67 

26.346 

33.5.32 

40.719 

47.905 

55.092 

62.278 

1.68 

26.568 

33.819 

41.071 

48.322 

55.573 

62.824 

1.69 

26.791 

34.107 

41.423 

48.739 

56.055 

63.371 

1.70 

27.014 

34.395 

41.776 

49.1.57 

56.538 

63.919 

1.71 

27.239 

»  34.685 

42.131 

49.577 

57.024 

64.470 

1.73 

27.463 

34.974 

42.486 

49.998 

57.509 

65.021 

1.73 

27.687 

35.265 

42.842 

50.419 

57.997 

65.574 

1.74 

27.913 

35.556 

43.199 

50.842 

58.485 

66.128 

1.75 

28.138 

35.847 

43.556 

51.265 

58.975 

66.684 

1.76 

28.364 

36.139 

43.914 

51.689 

59.465 

67.240 

1.77 

28.590 

36.4.32 

44.274 

52.115 

59.957 

67.798 

1.78 

28.817 

36.725 

44.633 

52.541 

60.449 

6S.358 

1.79 

29.045 

37.019 

44.994 

52.969 

60.944 

6S.919 

1.80 

29.272 

37.314 

45.356 

53..397 

61.439 

60.481 

1.81 

29.500 

37.609 

45.718 

53.827 

61.936 

70.043 

1.83 

29.729 

37.905 

46.081 

54.257 

62.433 

70.610 

1.83 

29.958 

38.201 

46.445 

54.689 

62.932 

71.176 

1.84 

30.187 

38.498 

46.809 

55.121 

63.432 

71.743 

1.85 

30.416 

38.798 

47.175 

55.554 

63.933 

72.312 

1.86 

30.646 

39.094 

47.541 

55.988 

64.435 

72.882 

1.87 

30.877 

39.392 

47.908 

56.423 

64.938 

73.454 

1.88 

31.108 

39.691 

48.275 

56.859 

65.443 

74.027 

1.89 

31.339 

39.991 

48.644 

57.296 

65.949 

74.601 

1.90 

31.571 

40.292 

49.013 

57.734 

63.455 

75.177 

l.Sl 

31.803 

40.593 

49.383 

58.173 

60.963 

75.753 

1.93 

32.035 

40.894 

49.753 

58.612 

67.472 

70.331 

1.93 

32.267 

41.196 

50.125 

59.053 

67.981 

70.910 

1.94 

32.501 

41.499 

50.497 

59.495 

68.493 

77.491 

1.95 

32.734 

41.802 

50.870 

69.937 

69.005 

78.073 

1.96 

32.968 

42.106 

51.243 

60.381 

69.518 

78.656 

1.97 

33.202 

42.410 

51.617 

60.825 

70.032 

79.240 

1.98 

33.437 

42.715 

51.992 

61.270 

70.518 

79.824 

1.99 

33.672 

43.020 

52.368 

61.716 

71.064 

80.412 

3.00 

33.907 

43.326 

52.745 

62.163 

71.582 

81.001 

30 


MEASURExMENT   OP  IRRIGATION   WATER. 


Table   1 — Discharge   of  standard   contracted   rectangular  weirs   in 
cubic  feet  per  second,  computed  from  the  formula  Q  =  3.33 

(L  —  .2H)   H%. .     {See  paragraphs  8  and  18.) 


Length  of  weir  L,  feet 

Length  of  weir  L,  feet. 

Head  H, 

Head  H, 

feet 

feet 

1 

5.0 

6.0 

7.0 

8.0 

9.0 

6.0 

7.0 

8.0 

9.0 

2.01 

43.632 

1 
53.122  62.601  72.091 

'  81.580 

2.51 

72.805 

86.047 

99.289 

112.531 

2.03 

43.939 

53.499  63.060i72.620 

82.180 

2.52 

73.212 

86.533 

99.864 

113.175 

2.03 

44.247 

53.878  63.509173.141 

82.772 

2.53 

73.625 

87.026: 100.427 

113.828 

2.04 

44.554 

54.257  63.959i73.662 

83.365 

2.54 

74.032 

87.512  100.992  114.472 

2.05 

44.863 

54.637, 64.411i74.185 

83.959 

2.55 

74.444 

88.004  i  101.564  116.124 

a.06 

45.172 

55.018  64.863  74.709 

84.555 

2.56 

74.856 

88.496' 102.136  115.776 

2.07 

45.481 

55.399  65.316  75.233 

85.151 

2.57 

75.26S 

8S.988i  102.708  116.428 

2.08 

45.791 

55.781  65.770  75.760 

85.749 

2.58 

75.679 

89.479  103.279  117.079 

2.09 

46.104 

56.166  66.228  76.290 

86.352 

2.59 

76.090 

89.970!  103.850  117.730 

2.10 

46.414 

56.548  66.6S2i76.S16 

86.950 

2.60 

76.506 

90.467!  104.428  118.389 

2.11 

46.723 

56.929  67. 135i77.341 

87.547 

2.61 

76.917 

90.957  104.999  119.039 

2.12 

47.037 

57.316  67. 595177.874 

88.153 

2.62 

77.332 

91.454  105.576  119.698 

2.13 

47.350 

57.702  68.054  78.406 

88.758 

2.63 

77.747 

91.9501106. 153  120.356 

2.14 

47.663 

58.088  68.513  78.938 

89.363 

2.64 

78.162 

92.4461106.730  121.014 

2.15 

47.976158.474168. 972179.470 

89.968 

2.65 

78.527 

92.8831107.239  121.595 

2.16 

48.2S815S.859  69.43080.001 

90.572 

2.66 

78.996 

93.443ll07.890|l22.337 

2.17 

48.605 

59.250  69.895  80.540 

91.185 

2.67 

79.410 

93.9381108.466 

122.994 

2.18 

48.917 

59.635  70.353  81.071 

91.789 

2.68 

79.829 

94.439!  109.049 

123.659 

2.19 

49.233 

60.025  70.817  81.609 

92.401 

2.69 

80.248 

94.9401109.632 

124.324 

2.20 

49.549 

60.415  71.281  82.147 

93.013 

2.70 

80.666 

95.440 

110.214 

124.988 

2.21 

49.865 

60.805  71. 745'82.685 

93.625 

2.71 

81.084 

95.940 

110.796 

125.652 

2.22 

50.184 

61.199  72.214183.229 

94.244 

^2.73 

81.502 

96.440 

111. .378 

126.316 

2.23 

50.499 

61. 5SS  72. 677183.766 

94.855 

2.73 

81.925 

96.945 

111.967 

126.987 

2.24 

50.819 

61.983  73. 147i84.311 

95.475 

2.74 

82.341 

97.445 

112.547 

127.651 

2.25 

51.137 

62.376i73.615 

84.854 

96.093 

2.75 

82.764 

97.950 

113.136 

128.322 

2.26 

51.456 

62.770,74.084 

85.398 

96.712 

2.76 

83.185 

98.455;ii3.723'12S.993 

2.27 

51.774 

63.16374.552 

85.941 

97.330 

2.77 

83.607 

98.959|114.311 

129.663 

2.28 

52.092 

63.556|75.020i86.484 

97.948 

2.78 

84.028 

99.463  114.898 

130.333 

2.29 

52.415 

63.955'75. 495187.035 

98.575 

2.79 

84.454 

99.973  115.4912 

131.011 

2.30 

52.732 

64.347175.962187.577 

99.192 

2.80 

84.875 

100.477  116.079 

131.681 

2.31 

53.054 

64.74576. 436I8S.127 

99.818 

2.81 

85.300 

100.986ill6.672 

132.359 

2.32 

53.375 

65.142  76. 909 1 88.676 

100.443 

2.82 

85.720 

101.4891117.258 

133.027 

2.33 

.53.696 

65.539'77. 382  89.225 

101.068 

2.83 

86.145 

101.998ill7.851 

133.704 

2.34 

.54.021 

65.941  77.861  89.781 

101.701 

2.84 

86.575 

102.513 1118.451 

134.389 

2.35 

54.342  66.338  78.334190.330 

102.326 

2.85 

86.999 

103.021  119.043 

135.065 

2.36 

54.667 

66.739178. 81390.885 

102.959 

2.86 

87.423 

103.529  119.635 

135.741 

2.37 

54.991 

67.141i79.291 

91.441 

103.591 

2.87 

87.852 

104.043!  120.2.34 

136.425 

2.38 

55.315 

67.542  79.769 

91.996 

104.223 

2.88 

88.276 

104.551  i  120.826 

137.101 

2.39 

,55.639 

67.943  80.247 

92.551 

104.8.55 

2.89 

88.704 

105.0641121.424 

137.784 

2.40 

55.962 

68.343  80.724 

93.105 

105.486 

2.90 

89.132 

105..577'122  022 

138.467 

2.41 

56.290 

68.749  81. 208'93.667 

106.126 

2.91 

89.559 

106.089  122.619 

139.149 

2.42 

56.613 

69.149  81. 685i94.221 

106.7.57 

2.92 

89.992 

106.608,123.224 

139.840 

2.43 

56.939 

69.553  82.167194.781 

107.395 

2.93 

90.419 

107.120  123.821 

140.522 

2.44 

57.266 

69.958  82.650i95.342 

108.034 

2.94 

90.851 

107.638 1 124.425 

141.212 

2.45 

57.593 

70.363  83.133195.903 

108.673 

2.95 

91.277 

108.149  125.021 

141.893 

2.46 

57.919 

70.767;83.615{96.463 

109.311 

2.96 

91.709 

lOf.667!  125.625 

142.683 

2.47 

58.249 

71.176  84.10397.030 

109.957 

2.97 

92.140 

109.184  126.228 

143.272 

2.4S 

.58.575 

7 1.579, 84.. 585!  97.589 

110.595 

2.98 

92.571 

109.701 1126.831 

143.961 

2.49 

58.904 

71.988  85.072  98.156 

111.240 

2.99 

93.006 

110.223 

127.440 

144.657 

2.60 

59.233 

72.397i85.5.59i98.723 

1                            1 

111.885 

3.00 

93.438 

110.741 

128.044 

146.348 

MEJASUREMENT    OF    IRRIGATION    WATER. 


31 


Table  1 — Discharge  of  standard  contracted  rectangular  weirs  in 
cubic  feet  per  second,  computed  from  the  formula  Q  =^  3.33 
(L  —  .3H)   H%.      (See  paragraphs  8  and  18.) 


Length  of  weir  L,  feet. 

Length  of  weir 
L,  feet. 

Length 
of  weir 

Head  H, 

Head  H. 

Head  H, 

L,  feet. 

feet 

1 

feet 

feet 

[  7.0 

8.0 

9.0 

1            ■** 

8.0 

9.0 

9.0 

3.01 

11L261  128.650 

146.040 

3.51 

159.812 

181.710 

4.01 

219.214 

3.03 

lll.737il29.207 

146.676 

3.52 

160.451 

182.443 

4.02 

219.981 

3.63 

112.300  129.864 

147.427 

3.53 

161.092 

183.178 

4.03 

220.750 

3.04 

112.821(130.471 

148.121 

3.54 

161.733  183.912 

4.04 

221.517 

3.05 

113.343  131.081 

148.818 

3.55 

162.373 

184.646 

4.05 

222.286 

3.06 

113.865  131.690 

149.514 

3.56 

163.016 

185.383 

4.06 

223.055 

3.07 

114.389  1.32.301 

150.213 

3.57 

163.657 

186.118 

4.07 

223.824 

3.08 

114.912  132.912 

150.912 

3.58 

164.301 

186.857 

4.C8 

224.595 

3.09 

11.5.435  133.523 

151.610 

3.59 

164.945 

187.595 

4.09 

225.341 

3.10 

115.959!  131. 134  152.310 

1   3.60 

165.588 

188.333 

4.10 

226.139 

3.11 

116.484:134. 747:153.011 

3.61 

166.233 

189.074 

4.11 

226.912 

3.12 

117.010  135. 36lll53.713 

3.62 

166.878 

189.813 

4.12 

227.684 

3.13 

117.536  135.976,154.416 

3.G3 

167.525 

190.555  1 

4.13 

228.458 

3.14 

118.064  136.592115.5.121 

3.64 

168.171 

191.297 

4.14 

229.232 

3.15 

118.590  137. 207!  155.824 

3.65 

168.817 

192.038 

4.15 

230.006 

3.16 

119.117 

137.823 

156.528 

3.66 

169.466 

192.782 

4.16 

230.782 

3.17 

119.846 

138.440 

157.235 

3.67 

170.113 

193.525 

4.17 

231.557 

3.1s 

120.1771139.0601157.944 

3.G8 

170.763  1194.271  1 

4.18 

232.333 

3.19 

120.704  139. 6771158.650 

3.69 

171.412  1195.016 

4.19 

233.110 

3.20 

121.234  140.295 

159.357 

3.70 

172.061  1 195.761 

4.20 

233.887 

3.21 

121.765  140.917 

160.068 

3.71 

172.713  196.509 

4.21 

234.667 

3.22 

122.296  141.537 

160.778  ' 

3.72 

173.363 

197.256 

4.22 

235.446 

3.23 

122.827!  142. 158 

161.489 

3.73 

174.014 

198.003 

4.23 

236.224 

3.24 

123.360ll42.780 

162.201 

3.74 

174.666 

198.751 

4.24 

237.005 

3.25 

123.892  143.402: 162.913! 

3.75 

175.318 

199.500 

4.35 

237.785 

3.26 

124.425;  144.026  163.G27 

3.76 

175.972 

200.251 

4.36 

238.565 

3.37 

124.9.59*144.650  164.341 

3.77 

176.625  '201.001 

4.27 

239.-348 

3.2s 

125.492  145.273  165.054 

3.78 

177.281  201.754 

4.28 

240.130 

3.29 

126.027;  145.8991 165.771 

3.79 

177.9.34  202.503 

4.29 

240.914 

3.30 

126.562  146.5241 166.486 

3.80 

178.591  203.259 

4.30 

241.698 

^.31 

127.098  147.1511167.204 

3.81 

179.245  ,204.010 

4.31 

242.481 

3.32 

127.634!  147.778 

167.922 

3.82 

179.902  204.764 

4.33 

243.267 

3.33 

128.171  148.406 

168.642 

3.83 

180.561 

205..521 

4.33 

214.053 

3.34 

128.709  149.035 

169.362 

3.84 

181.217 

206.274 

4.34 

244.837 

3.33 

129.245!l49.663  170.081 

3.S5 

181.874  ,207.030 

4.35 

245.67D 

3.36 

129.7841 150.294' 170.803 

3.86 

182.534  1207.787 

4.36 

246.411 

3,37 

130.323  150.924  171.525 

3.87 

183.193  208.545 

4.37 

247.197 

3.38 

130.863: 151.555  172.249 

3.88 

183.8.52 

209.302 

4.38 

247.986 

3.39 

131.402  152.187 

172.972 

3.89 

184.513 

210.062 

4.39 

248.774 

3.40 

131.947  1.52.825 

173.702 

3.90 

185.173 

210.821 

4.40 

249.562 

3.41 

132.482  153.451 

174.420 

3.91 

185.834 

211..5S0 

4.41 

250.352 

3.43 

133.023  154.084 

175.146 

3.93 

186.713 

212.587 

4.42 

251.141 

3.43 

133.565: 154.719 

175.873 

3.93 

187.158 

213.101 

4.43 

251.934 

3.44 

134.107  1.55.3541176.600  | 

3.94 

187.821 

213.864 

4.44 

252.725 

3.45 

134.649 

155.988 

177.327 

3.95 

188.485 

214.627 

4.45 

253.516 

3.46 

135.192 

156.624 

178.056 

3.96 

189.148 

215.389 

4.46 

254.307 

3.47 

13.5.735 

157.260 

178.785 

3.97 

189.813 

216.154 

4.47 

255.100 

3.48 

136.280 

157.898 

179.516 

3.98 

190.477 

216.918 

4.48 

255.859 

3.49 

136.825 

158.536 

180.247 

3.99 

191.142 

217.682 

4.49 

256.637 

3.30 

137.368 

159.173 

180.977 

4.00 

191.808 

218.448 

4.50 

257.481 

32 


MEASUREMENT   OF   IRRIGATION   WATER. 


Table  2. — Discharge  of  standard  Cippoletli  and  standard  suppressed 
rectangular  weirs  in  cubic  feet  per  second.  Values  below  and 
to  left  of  heavy  line  deiermined  experimentally;  others  com- 
puted from  the  formula  Q  =  3.367  L  H  \  .   (See  paragraphs 


10, 

12  ( 

2nd   19.) 

Length  of  weir  L,  feet. 

Head  //, 

feet 

#> 

0.5 

1.0 

1.5 

2.0 

3.0 

4.0 

5.0       6.0 

7.0 

8.0 

9.0 

«.01 

0.002 

0.003 

0.005 

0.007 

0.010 

0.013 

0.017 

0.020 

0.024 

0.027 

0.030 

.02 

.005 

.010 

.014 

.019 

.029 

.038 

.048 

.057 

.067 

.076 

.086 

.US 

.009 

.018 

.026 

.035 

.053 

.070 

.087 

.105 

.123 

.140 

.157 

.04 

.013 

.027 

.040 

.054 

.081 

.108 

.135 

.162 

.189 

.215 

.242 

.05 

.019 

.038 

.057 

.075 

.113 

.151 

.188 

.220 

.263 

.301 

.339 

.06 

.025 

.050 

.074 

.099 

.148 

.198 

.247 

.297 

.346 

.396 
.•499 

.445 

.07 

.031 

.062 

.093 

.125 

.187 

.249 

.312 

.374 

.437 

.561 

.08 

.038 

.076 

.114 

.152 

.229 

.305 

.381 

.457 

.633 

.609 

.686 

.0» 

.045 

.091 

.136 

.182 

.273 

.364 

.455 

.545 

.636 

.727 

.818 

.10 

.053 

.107 

.160 

.213 

.319 

.426 

.532 

.639 

.745 

.852 

.958 

.11 

.061 

.123 

.184 

.246 

.369 

.491 

.614 

.737 

.8601     .983 

1.105 

.12 

.070 

.140 

.210 

.280 

.420 

.560 

.700 

.840 

.980 

1.120 

1.259 

.13 

.079 

.158 

.237 

.316 

.473 

.631 

.789 

.947 

1.106 

1.202 

1.420 

a* 

.088 

.176 

.265 

.353 

.529 

.705 

.882 

1.058 

1.245 

1.411 

1.587 

AS 

.098 

.196 

.293 

.391 

.587 

.782 

.978]   1  173 

1.369    1.565 

1.760 

A6 

.108 

.216 

.323 

.431 

.646 

.862 

1.077 

1.293 

1.508]   1.724 

1.939 

A7 

.118 

.236 
.257 

.354 
.386 

.472 
.514 

.708 
.771 

.944 
1.028 

1.180 
1.285 

1.416 
1.543 

1.652    1.SS8 
1.800'  2.057 

2.124 

.18 

.129 

2.314 

.19 

.139 

.279 

.418 

.558 

.837 

1.115 

1.394 

1.673 

1.9521  2.231 

2.509 

.29 

.151 

.301 

.452 

.602 

.903 

1.205 

1.506 

1.807 

2.108J  2.409 

2.710 

.21 

.162 

.324 

.486 

.648 

.972 

1.296 

1.620 

1.944 

2.268    2.592 

2.916 

.22 

.174 

.347 

.521 

.695 

1.042 

1.390 

1.737 

2.084 

2.432i   2.779 

3.127 

.23 

.186 

.371 

.557 

.743 

1.114 

1.485 

1.857 

2.228 

2.599i  2.971 

3.342 

.24 

.200 

.396 

.594 

.792 

1.187 

1.583 

1.979 

2.375i   2.771;  3.167 

3..563 

.25 

0.214 

.421 

.631 

.842 

1.263 

1.683 

2.104 

2.525 

2.946'  3.367 

3.787 

.2S 

.446 

.669 

.893 

1.339 

1.785 

2.232 

2.678 

3.124!  3.571 

4.017 

.27 

.472 

.709 

.945 

1.417 

1.889 

2.362 

2.834 

3.306 

3.779 

4.251 

.28 

.499 

.748 

.998 

1.496 

1.995i   2.494 

2.993 

3.492 

3.991 

4.4S9 

.29 

.526 

.789 

1.051 

1.577 

2.103 

2.629 

3.155 

3.680 

4.200 

4.732 

.30 

.553 

.830 

1.106 

1.660 

2.213 

2.766 

3.319 

3.872!  4.426 

4.979 

.31 

.581 

.872 

1.162 

1.743 

2.324 

2.905 

3.487 

4.06Si  4.649 

5.230 

.32 

.609 

.914 

1.219 

1.828 

2.438 

3.047 

3.057 

4.2G6i  4.875 

5.486 

.33 

.638 

.957 

1.276 

1.915 

2.553 

3.191 

3.829!  4.467 

5.100 

6.744 

.34 

.067 

1.001 
1.046 

1.335 
1.394 

2.002 
2.091 

2.670 
2.788 

3.337 
3.486 

4.005 
4.183 

4.672 

4.880 

5.340 
6.577 

6.007 

.35 

.697 

6.274 

.88 

.727 

1.091 

1.4.'54 

2.182 

2.909 

3.636 

4.363 

5.090 

6.818 

6.545 

.37 

.758 

1.137 

1.515 

2.273 

3.031 

3.789 

4.546 

5.304 

6.062 

6.819 

.38 

.789 

1.183 

1.577 

2.366 

3.155 

3.943 

4.732 

5.520,   6.309 

7.098 

.39 

.82Q 

1.230 

1.640 

2.460 

3.280 

4.100 

4.920 

5.740    6.560 

7.380 

.49 

.852 

1.27S 

1.703 

2.555 

3.407 

4.259 

5.110 

5.962 

6.814 

7.665 

.41 

.884 

1.326 

1.768 

2.651 

3.535 

4.419 

5.303 

6.187 

7.071 

7.965 

.42 

.916 

1.375 

1.833 

2.749    3.665 

4.582 

5.498 

6.415 

7.331 

8.247 

.43 

.949 

1.424 

1.899 

2.848 

3.797 

4.747 

6.690 

6.645 

7.594 

8.  .544 

.44 

.983 

1.474 

1.965 

2.948 

3.930 

4.913 

6.896 

6.878 

7.861 

8.843 

.45 

1.016 

1.524 

2.033 

3.049 

4.065 

6.0s  1 

6.098 

7.114 

8.130 

9.147 

.46 

1.050 

1.575 

2.101 

3.151 

4.201 

5.252 

6.302 

7.363 

8.403 

9.453 

.47 

1.0S5 

1.627 

2.170 

3.254 

4.339 

6.424 

6.509 

7.594 

8.678 

9.763 

.48 

1.122 

1.679 

2.239 

3.359 

4.478 

5.  .598 

6.718 

7.837 

8.957 

10.076 

.49 

1.161 

1.732 

2.309 

3.464 

4.619 

6.774 

6.929 

8.083 

9.238 

10.393 

0.50 

1.200 

1.785 

2.381 

3.571 

4.761 

5.951 

7.142 

8.332 

9.522 

10.713 

MEASUREMENT  OF   IRRIGATION   WATER. 


oo 


Table  8 — Discharge  of  standard  Cippoletti  and  standard  suppressed 
rectangular  weirs  in  cubic  feet  per  second.  Values  below  and 
to  left  of  heavy  line  determined  experimentally;  others  com- 
puted from  the  formula  Q  =  3.367  L  H\  .  {See  paragraphs 
10,  12  and  19.) 


Head  //, 
feet 


Length  of  weir  L,  feet. 


1.5       2.0        3.0         4.0 


5.0 


6.0 


8.0  9.0 


0.51 
.&% 
.63 
.54 
.55 
.66 
.57 
.58 
.59 
.60 
.61 
.63 
.63 
.64 
.G.5 
.66 
.67 

.68 
.69 
.70 
.71 
.73 
.73 
.74 
.75 

.76 
.77 

.78 
.79 
.SO 
.81 
.83 
.83 
.84 
.85 
.86 
.87 
.88 
.89 
.90 
.91 
.93 
.93 
.94 
.95 
.96 
.97 
.93 
.99 
l.CO 


1.S30 

2.451| 

1.891 

2.5251 

1.949 

2.698 

2.004 

2.672 

2.060 

2.747 

2.116 

2.822 

2.173 

2.89S 

2.231 

2.974 

2.289 

3.051 

2.347 

3.129 

2.406 

3. 208 

2.465 

3.287 

2.525 

3.367 

2.. 586 

3.447 

2.646 

3.529 

2.708 

3.610 

2.769 

3.693 

2.832 
2.894 
2.9.58 
3.021 
3.085 
3.150 
3.215 
3.2Sn 


3.810 

3.895 

3.980 

4.06 

4.15 

4.24 

4.33 

4.415 

4.51 

4.60 

4.69 

4.78 

4.87 

4.96 

5.05 

5.14 

5.24 

5.34 

5.44 

5.64 

5.64 

5.74 

5.84 

5.94 

6.04 

6.14 

6.25 

6.36 

6.47 

6.58 

6.69 

6.80 

6.91 


3.679 

4.905 

6.131 

7.357 

3.787 

5.050 

6.312 

7.575 

3.897 

5.196 

6.495 

7.794 

4.008 

5.344 

6.680 

8.016 

4.120 

5.493 

6.866 

8.239 

4.233 

6.643 

7.054 

8.465 

4.346 

5.795 

7.244 

8.693 

4.461 

6.948 

7.435 

8.923 

4.. 577 

6.103 

7.629 

9.154 

4.694 

6.259 

7.823 

9.388 

4.812 

6.416 

8.020 

9.624 

4.931 

6.574 

8.218 

9.861 

5.051 

6.734 

8.417 

10.101 

5.171 

6.895 

8.619 

10.342 

5.293 

7.057 

8.821 

10.586 

5.415 

7.221 

9.026 

10.831 

5.539 

7.386 

9.232 

11.078 

5.663 

7.551 

9.439 

11.327 

5.789 

7.719 

9.64S 

11.578 

5.915 

7.887 

9.859 

11.830 

6.042 

8.057 

10.071 

12.085 

6.171 

S.227 

10.284 

12.341 

6.299 

8.399 

10.499 

12.599 

6.429 

8.573 

10.716 

12.859 

6.560 

8.747 

10.934 

13.120 

6.692 

8.922 

11.153 

13.384 

6.824 

9.099 

11.373 

13.649 

6.958 

9.277 

11.596 

13.915 

7.092 

9.456 

11.820 

14.184 

7.227 

S.636 

12.045 

14.454 

7.363 

9.817 

12.271 

14.726 

7.500 

10.000 

12.499 

14.999 

7.637 

10.183 

12.729 

15.275 

7.776 

10.368 

12.959 

15.551 

7.915 

10.553 

13.192 

15.830 

8.055 

10.740 

13.425 

16.110 

8.196 

10.928 

13.660 

16.392 

8.338 

11.117 

13.896 

16.675 

8.480 

11.307 

14.134 

16.960 

8.623 

11.498 

14.373 

17.247 

8.768 

11.690 

14.613 

17.535 

8.913 

11.883 

14.854 

17.825 

9.058 

12.078 

15.097 

18.117 

9.205 

12.273 

15.341 

18.410 

9.352 

12.469 

15.587 

18.704 

9.500 

12.667 

15.833 

19.000 

9.649 

12.865 

16.081 

19.298 

9.799 

13.065 

16.331 

19.597 

9.949 

13.265 

16.581 

19.898 

0.100 

13.467 

16.833 

20.200 

8.583 

8.837 

9.093 

9.352 

9.613 

9.876 

10.142 

10.410 

10.680 

10.953 

11.228 

11.505 

11.784 

12.066 

12.350 

12.636 

12.924 

13.215 
13.507 
13.802 
14.099 
14.398 
14.699 
15.002 
15.307 
15.614 
15.923 
16.235 
16.548 
16.863 
17.180 
17.499 
17.820 
18.143 
18.468 
18.795 
19.124 
19.465 
19.787 
20.122 
20.468 
20.796 
21.136 
21.478 
21.821 
22.167 
22.514 
22.863 
23.214 
23.5671 


9.809 
10.099 
10.392 
10.688 
10.986 
11.287 
11.591 
11.897 
12.206 
12.517 
12.832 
13.149 
13.468 
13.790 
14.114 
14.441 
14.771 
15.103 
15.437 
15.774 
16.113 
16.455 
16.799 
17.145 
17.494 
17.845 
18.198 
18.554 
18.912 
19.272 
19.634 
19.999 
20.366 
20.735 
21.107 
21.480 
21.858 
22.234 
22.614 
22.996 
23.380 
23.767 
24.155 
24.546 
24.939 
25.334 
25.731 
26.129 
26.530 
26.933 


11.036 
11.362 
11.691 
12.024 
12.359 
12.698 
13.039 
13.384 
13.761 
14.082 
14.436 
14.792 
15.151 
15.514 
15.879 
16.247 
16.617 

16.991 
17.367 
17.746 
18.127 
18.611 
18.899 
19.2S8 
19.680 

20.075 
20.473 
20.873 
21.276 
21.681 
22.089 
22.499 
22.912 
23.327 
23.745 
24.165 
24.588 
26.013 
26.441 
25.871 
26.303 
26.738 
27.175 
27.614 
28.056 
28.500 
28.947 
29.395 
29.847 
30.300 


34 


MEASUREMENT   OF   IRRIGATION   WATER. 


Table  2 — Discharge  of  standard  Cippoletti  and  standard  suppressed 
rectangular  weirs  in  cubic  feet  per  second.  Values  below  and 
to  left  of  heavy  line  determined  experimentally ;  others  com- 
puted from  the  formula  Q  =  3.367  L  Hi.  (See  paragraphs 
10,  12  and  19.) 


Length  of  wcir  L,  feet. 

Head  //. 

feet 

3.0 

4.0 

5.0 

CO 

7.0 

8.0 

9.0 

1.01 

10.46 

13,671 

17.089 

20.504 

23.921 

27.338 

30.756 

i.oa 

10.62 

13.874 

17.343 

20.809 

24.277 

27.745 

31.213 

1.03 

10.78 

14.079 

17.599 

21.116 

24.635 

28.1,54 

31.674 

1.04 

10.94 

14.284 

17.855 

21.424 

24.995 

28.565 

32.136 

1.05 

11.10 

14.490 

18.113 

21.734 

25.356 

28.978 

32.601 

1.06 

11.20 

14.698 

18.373 

22.045 

25.719 

29.393 

33.067 

1.07 

11.42 

14.907 

18.033 

22.358 

26.084 

29.810 

33.537 

1.08 

11. .58 

15.116 

18.895 

22.672 

26.451 

30.229 

34.008 

1.09 

11.74 

15.326 

19.158 

22.987 

26.819 

30.650 

34.481 

1.10 

11.90 

15.538 

19.423 

23.305 

27.189 

31.073 

34.957 

1.11 

12.06 

15.750 

19.688 

23.623 

27.560 

31.497 

35.435 

1.12 

12.22 

15.964 

19.955 

23.943 

27.933 

31.924 

35.915 

1.13 

12.38 

16.178 

20.222 

24.264 

28.308 

32.353 

36.397 

1.14 

12.54 

16.393 

20.491 

24.587 

28.685 

32.783 

36.881 

1.15 

12.71 

16.609 

20.761 

24.911 

29.063 

33.215 

37.367 

1.16 

12.88 

16.826 

21.033 

25.237 

29.443 

33.649 

37.856 

1.17 

13.05 

17.044 

21.305 

25.564 

29.825 

34.085 

38.346 

1.18 

13.22 

17.263 

21.579 

25.893 

30.20S 

34.523 

38.839 

1.19 

13.39 

17.483 

21.854 

26.222 

30.593 

34.963 

39.333 

1.20 

13.56 

17.704 

22.1.30 

26.554 

30.970 

35.405 

39.830 

1.21 

13.73 

17.926 

22.407 

26.888 

31.367 

35.848 

40.329 

1.22 

13.91 

18.149 

22.686 

27.223 

31.757 

36.294 

40.830 

1.23 

14.09 

18.372 

22.965 

27.559 

32.148 

36.741 

41.333 

1.24 

14.27 

18.597 

23.246 

27.895 

32.544 

37.194 

41.843 

1.25 

14.45 

18.822 

23.527 

28.233 

32.939 

37.644 

42.349 

1.26 

14.63 

19.048 

23.811 

2S.573 

33.335 

38.097 

42.859 

1.27 

14.81 

19.276 

24.095 

28.913 

33.732 

38.551 

43.370 

1.28 

14.99 

19.504 

24.380 

29.456 

34.132 

39.008 

43.874 

1.29 

15.17 

19.733 

24.666 

29.599 

34.532 

39.466 

44.399 

1.30 

15.35 

19.962 

24.953 

29.944 

34.934 

39.925 

44.915 

1.31 

15.53 

20.154 

25.242 

30.290 

35.339 

40.307 

45.436 

1.32 

15.71 

20.425 

25.531 

30.638 

35.744 

40.850 

45.957 

1.33 

15.89 

20.658 

25.822 

30.986 

36.151 

41.315 

46.480 

1.34 

16.07 

20.891 

26.114 

31.337 

36.560 

41.782 

47.005 

1.35 

16.25 

21.125 

26.407 

31.688 

36.969 

42.250 

47.532 

1.36 

16.44 

21.360 

26.701 

32.041 

37.381 

42.721 

48.061 

1.37 

16.63 

21.596 

26.995 

32.394 

37.793 

43.192 

48.591 

1.38 

16.82 

21.834 

27.292 

32.750 

38.209 

43.667 

49.126 

1.39 

17.01 

22.071 

27.589 

33.121 

38.625 

44.142 

49.660 

1.40 

17.20 

22.310 

27.887 

33.465 

39.043 

44.620 

50.197 

1.41 

17.39 

22.549 

28.187 

33.824 

39.401 

45.098 

50.736 

1.42 

17.58 

22.790 

28.487 

34.184 

39.882 

45.579 

51.277 

1.43 

17.77 

23.031 

28.789 

34.546 

40.304 

46.062 

51.819 

1.44 

17.96 

23.272 

29.091 

34.909 

40.727 

46.545 

52.363 

1.45 

18.15 

23.516 

29.395 

35.273 

41.152 

4-7.031 

52.910 

1.46 

18.34 

23.759 

29.699 

35.639 

41.579 

47.518 

53.458 

1.47 

18.53 

24.004 

30.005 

36.005 

42.006 

48.007 

54.008 

1.48 

18.72 

24.249 

30.311 

30.374 

42.436 

48.498 

54.501 

1.49 

18.91 

24.495 

30.619 

36.743 

42.867 

48.990 

55.114 

1.50 

19.10 

24.742 

30.928 

37.114 

43.299 

49.485 

55.669 

MEASUREMENT   OF   IRRIGATION   WATER. 


35 


Table  2 — Discharge  of  standard  Cippoletti  and  standard  suppressed 
rectangular  weirs  in  cubic  feet  per  second,  computed  from 

the  formula   Q  =  3.367   L  //I.       {See  paragraphs  10,   12 
and  19.) 


1 
1 

Length  of  weir  L,  feet. 

Head  H,        \ 

feet 

1 

4.0 

5.0 

6.0 

7.0 

8.0 

9.0 

1.51 

24.990 

31.238 

37.486 

43.733 

49.981 

56.228 

1.52 

25.239 

31.. 549 

37,858 

44,168 

50.478 

56.787 

1.53 

25.479 

31.849 

38.219 

44.589 

50.958 

57.328 

1.64 

25.738 

32.173 

38.608 

45.042 

51.477 

57.911 

1.55 

25.990 

32.487 

3S,9S4 

45.482 

51.979 

58.477 

1.56 

26.242 

32.802 

39.362 

45.923 

52.483 

58.944 

1.57 

26.494 

33.118 

39.742 

46,365 

52.989 

59.612 

1.58 

26.748 

33.435 

40.122 

46,809 

53,496 

60.183 

1.59 

27.002 

33.753 

40.504 

47,2.54 

54,005 

60.755 

1.60 

27.253 

34.066 

40.879 

47.692 

54.506 

61.319 

1.61 

27.513 

34.391 

41.270 

48.148 

55.025 

61.906 

1.62 

27.770 

34.713 

41.655 

48.597 

55.. 540 

62.483 

1.63 

28.028 

35.035 

42,041 

49.048 

56.055 

63.062 

1.64 

28.286 

35.357 

42,428 

49.500 

56.571 

63.623 

1.65 

28.545 

35.681 

42,817 

49.953 

57.090 

64.226 

1.66 

28.805 

36.006 

43,207 

50,408 

57.610 

64.811 

1.67 

29.066 

36.332 

43,598 

50,865 

58.131 

65.398 

1.68 

29.327 

36.659 

43.991 

51.323 

58.654 

65.986 

1.69 

29.589 

36.987 

44.384 

51.781 

59.178 

66.576 

1.70 

29.852 

37.315 

44.778 

52.241 

59.704 

67.167 

1.71 

30.116 

37.645 

45,174 

52.703 

60.232 

67.761 

1.73 

30.381 

37.976 

45.571 

53.196 

60.762 

6S.357 

1.73 

30.646 

38.307 

45.969 

53.631 

61.292 

68.9.53 

1.74 

30.912 

38.640 

46.368 

54.096 

61.824 

69.552 

1.75 

31.075 

38.969 

46.583 

54.557 

62.150 

70.144 

1.76 

31.446 

39.308 

47.170 

55.031 

62.893 

70.754 

1.77 

31.715 

39.643 

47.572 

55..501 

63,430 

71.358 

1.78 

31.984 

39.980 

47.976 

55,972 

63,938 

71.964 

1.79 

32.254 

40.317 

48.383 

56,445 

64,508 

72.571 

1.80 

32.524 

40.655 

48.787 

56,918 

65.049 

73.  ISO 

1.81 

32.796 

40.995 

49.194 

57..393 

65,592 

73.791 

1.82 

33.0G8 

41.335 

49.602 

57,869 

66.136 

74-403 

1.83 

33.341 

41.677 

50,012 

58,347 

66.682 

75.018 

1.84 

33.614 

42.018 

50,422 

58,825 

67.229 

75.632 

1.85 

33.889 

42.361 

50.834 

59,306 

67.778 

76.251 

1.86 

34.164 

42.705 

51.247 

59.788 

68.-329 

76.870 

1.87 

34.440 

43.050 

51.660 

60.270 

68,580 

77.490 

1.88 

34.717 

43.396 

52.075 

60.754 

69,434 

78.113 

1.89 

34.994 

43.743 

52.491 

61.239 

69,988 

78.737 

1.90 

35.272 

44.091 

52.909 

61.727 

70.545 

79.003 

1.91 

35.551 

44.439 

53.327 

62.215 

71.102 

79.990 

1.92 

35.830 

44.788 

53.746 

62.703 

71.661 

80.618 

1.93 

36.111 

45.139 

54.166 

63.194 

72.222 

81.249 

1.94 

36.392 

45,490 

54.588 

63,686 

72.784 

81.882 

1.95 

36.674 

45.842 

55.010 

64.179 

72.347 

82.516 

1.96 

36,956 

46.195 

55.434 

64.673 

73.912 

83.142 

1.97 

37.239 

46.549 

55.869 

65.169 

74.478 

83.788 

1.98 

37.523 

46.904 

56.285 

65,666 

75.046 

84.427 

1.99 

37.808 

47.260 

56.712 

66,164 

75.616 

85.068 

2.00 

38.094 

47.617 

57.140 

66.664 

76.187 

85.711 

36 


MEASUREMENT   OF   IRRIGATION   WATER- 


Table  2 — Discharge  of  standard  Ctppoleiti  and  standard  suppressed 
rectangular  weirs  in   cubic  feet  per  second,  computed  from 

the   formula   Q   =   3.367   L   H^.       (See   paragraphs   10,    12 
and  19.) 


Length  of  weir  L,  feet. 


5.a       6.0       7.0 


47.974157. 

48.333157 

48.692;5S 

49.052  58 

49.413'59 

49.775  59 

50.138  60 

50.502 

50.809 

51.225 

51.597 

51.966 

52.335 1 62 

.52.704163 

53.073;  63 

53.443164 

53.817164 

54.185165 

•54.559165 

54.930 '65 

.55.307i66 

•55.687 1 66 

.56.061  67, 

•56.440:67, 

56.819I6S, 

57.199i68. 

57.57769 

57.9.57,69 

.58.34170 

.58.715:70 

59.105  70 

.59.489171 

.39.873  71 

60.26272. 

60.647172, 

61.035173 

6I.425I73, 

61.S15i74, 

62.203174 

6.2.58575, 

62.98775 

63.377  76 


56967, 
999:67, 


63.771 
64.165 
64.559 
64.953  77, 
65.3.53  78 
65.747  78 
66.147  79 
66.540  79 


,430 
,862 
,296 
731 
166 
602 
043 
,470 
916 
3.59 
803 
245 
638 
131 
580 
023 
471 
916 
369 
764 
273 
728 
183 
638 
093 
518 
009 
458 
925 
336 
848 
314 
776 
243 
710 
177 
644 
102 
581 
052 
525 
998 
471 
,944 


63, 

63 

69, 

69, 

70 

70 

71, 

71, 

72, 

72, 

73, 

73, 

74, 

74, 

75, 

75, 

76, 

76. 

77. 

77. 

78. 

79. 

79. 

80 

SO. 

;^1 

81. 

S2 

si 

S3. 

83 

84 

84 

85 

85. 

86. 

87. 

87. 

88. 

38. 

89. 

89, 

90, 

90, 


424  91 
897  92 
37692 
848:93 


164 

665 
169 
673 
,179 
086 
193 
703 
,217 
715 
236 
752 
,270 
,786 
302 
819 
.343 
860 
383 
902 
431 
982 
485 
016 

47 
078 
()09 

40 
077 
201 

46 
284 
822 

67 
885 
450 
995 
540 
085 
019 
182 
727 
279 
831 
383 
935 
494 
047 


8.0 


9.0 


Head 
H, 
feet 


Length  of  weir  L,  feet. 


6.0 


76. 

77. 

77. 

78. 

79. 

79. 

80. 

80. 

81. 

81. 

82, 

83, 

83. 

84. 

84. 

85. 

86. 

86. 

87. 

87. 

88. 

89. 

89. 

90. 

90. 

91. 

92. 

92. 

93. 

93. 

94, 

95 

95, 

96, 

97, 

97, 

98, 

98, 

99, 
100, 
100. 
101. 
102. 
102. 
103. 
103. 
104. 
10.5. 


758 
332 
907 
483 
062 
,041 
221 
803 
390 
960 
555 
146 
737 
326 
917 
508 
106 
097 
295 
888 
492 
099 


86.; 
86.! 
87.i 
88.; 
88.' 
89. 
90.; 
90.' 
91. 
92.: 

92.; 
93. 
94.: 
94.: 
95., 
96. 
98.: 
97.. 
98.: 
98.; 

99.. 

100.: 


(>9S!100.S 


006  105 
156  106 


304 
911 
518 
124 
731 
340 
044 
507 
182 
797 
419 
034 
657 
280 
903 
526 
136 
779 
402 
033 
604 
295 
926 
505 
196 
835 
4G4 


101. 
102.: 
102.' 
103.' 
104.: 
105.1 
105.' 
100.: 
107.1 
107.' 
108.' 
109. 
109.: 
llO.i 
111. 
111. 
112.1 
113.: 
114. 
114. 
115. 
116.: 

116.; 

117.1 

118.: 
119.1 
119.' 


353 

3.51 

999 

3.53 

646 

3.5;t 

294 

a.54 

944 

2.55 

596 

3.56 

248 

3.-57 

904 

3.58 

564 

3.59 

205 

3.00 

875 

3.01 

539 

3.63 

204 

3.63 

867 

3.64 

531 

3.65 

197 

3.66 

870 

3.67 

534 

8.68 

207 

3.69 

874 

3.70 

553 

3.71 

237 

3.73 

910 

3.73 

592 

3.74 

275 

3.75 

957 

3.76 

639 

3.77 

323 

3.78 

014 

3.79 

087 

2.80 

38.S 

3.81 

079 

3.83 

771 

3.83 

472 

3.84 

164 

3.86 

864 

3.86 

565 

3.87 

260 

3.88 

966 

3.89 

653 

3.90 

377 

3.91 

078 

3.93 

787 

3.93 

497 

3.94 

207 

3.95 

910 

3.96 

635 

3.97 

345 

3.98 

045 

3.99 

772 

3.00 

80. 

80, 

81. 

81. 

82. 

82. 

83. 

83. 

SI. 

84. 

85. 

85. 

SO. 

80. 

87. 

87. 

88. 

S3. 

89, 

S9, 

90, 

90, 

91, 

91, 

92, 

92. 

93, 

93, 

94, 

94. 

95, 

95, 

90, 

96, 

97, 

97, 

93. 

93, 

99, 

99, 

100, 

100. 

101. 

101. 

102, 

102, 

103, 

103, 

104, 

104. 


335 
814 
299 


7.0 


8.0 


9.0 


93. 

94, 
94, 


724  107, 


779  95 
264  95 

74  9  j 
2.34; 
720 1 


205 

684 
IS2I 
6731 


90. 
97. 
97. 

98. 
98. 
99. 
99. 


165  100, 
650  101. 
093  101. 
645;  102. 
136  102. 
027  103. 
131  103. 
616  104. 
127  105. 
02i  105. 
127  106. 
025  100. 
123  107. 
632  108. 
136  108, 
6;i9:l09, 
148  109, 
644  110. 
162  111. 
665;  HI. 
175,112. 
691  112. 
200  113. 


107, 
103 
109, 
109, 
110 
110 
111 
112 
112 
113 
114, 


283 

849 

409 

975 

541 

107 

673 

239 

798 

379 

952 

5201114 

099|115 

609  110 
116 
117 
118 

na 

552:119 
1481120 
72S  120 
315  121 
890  122 
483  122 
071 1 123 
658' 124 
2451 124 
840  125 
418  126 
022: 120 
6091 127 
204!  123 
800 1 123 


253 
820 
393 
930 


120.502 

121.221 

121.949 

122.008 

123.396 

124.123 

124.852 

125..580 

120.308 

127.026 

127.773 

128.610 

129,247 

129.984 

130,039 

860:131.407 

516,132.205 

.170  i;!2.941 

.842' 133.097 

4S8i  134.424 

.169113,5.190 

832' 13.5.930 

503!  130.700 

.166  137.437 

838  138.192 

510:138.948 

18l|l39.703 

852  140.459 


118 
752 
399 
038 
686 
332 
979 
626 
274 
912 
.676 
.231 
886 
554 
.124 


709 
226 
735 
251 
756 
282 
804 
320 
841 
357 
878 
400 
922 
450 
964 


113 
114 
115 
115 
110 
110 
117 
118 
US 
119, 
120, 
120 
121 
121 
122 


400 
994 
590 


129 
130 
130 


1911131 
793' 1:^2 
33211.33 
990' 133 
004 1 134 
200  135 
815  135 
4171 130 
025  137 
03411,37 
242  13,-J 
S,-)8  139 
458  139 


531 
.192 
882 
554 
.233 
921 
000 
279 
967 
.640 
334 
.008 
.710 
405 
093 
788 
476 
171 
8(57 
5(i2 
260 
952 


141.223 
141.060 
1-12.743 
143.498 
144.262 
145.036 
145.800 
146.564 
147.338 
143.102 
143.876 
149.034 
1 .50.423 
151.205 
151.979 
152.761 
153.535 
154.318 
155.101 
1.5,5.883 
150.666 
157.446 


MEASUREMENT   OF   IRRIGATION    WATER. 


m 


Table  2 — Discharge  of  standard  Cippoletti  and  standard  suppressed 
rectangular  weirs   in   cubic  feet  per  second,   computed  from 


the  formula   Q 
and  19.) 


3.367   L   H% .       {See  paragraphs   10,    13 


Head  H, 

feet 


Length  of  weir  L,  feet. 


7.0 


8.0 


9.0 


Head  H, 

feet 


Length  of 
weir  L,  feet. 


8.0 


9.0 


I  Length 
of 

Head//,   feet, 
feet 


9.0 


I 


3.01 

.3.02 

3.03 

3.0A 

3.G.5 

S.OC 

3.07 

3.«8 

3.ft9 

3.10 

3.11 

3.13 

3.13 

3.14 

3.15 

3.16 

g.l7 

3.18 

3.19 

3.30 

3.;J1 

3.23 

3.23 

3.24 

3.35 

3.36 

3.37 

3.28 

3.29 

3.30 

3.31 

3.32 

3.33 

3.34 

3.35 

3.36 

3.37 

3.38 

3.39 

8.40 

3.41 

3.43 

3.43 

3.44 

8.45 

3.46 

3.47 

3.48 

3.49 

3.50 


123.082 

12.'H.649 

124.309, 

124.925 

125.643 

126.130 

126.7S0; 

127.400 

128.020i 

128.632' 

129.264 

129.889 

130.514 

131.141 

131.767 

132.394 

13:^.023 

1.33.655 

134.2851 

134.9041 

135.5501 

13G.184; 

136.8191 

137.455 

1.38.091' 

138.729] 

139.369 

140.007 

140.648 

141.2741 

141.&33! 

142.576: 

143.221 

143.868 

144.514 

145.162 

145.810 

146.460 

147.111 

147.749 

148.414, 

149.067 

149.722 

150.377; 

151.033 

151.690 

152.348 

153.007 

153.667 

154.315 


M0.G65 

141.311, 

142.06Si 

142.771 

143.478 

144.183 

144.891! 

145.600] 

146.309 

147.008 

147.730 

148.444 

149.158 

149.875 

150.591 

151.307 

152.020 

152.749 

153.408 

1.54.176 

154.914 

155.G3S 

156.304 

157.091 

157. 8]8 

158.548 

159.278 

160.008 

160.741 

161.4.56 

102.209 

162.944 

163.682 

164.421 

165.168 

165.899 

160.640 

167.383 

168.126 

168.856 

169.616 

170.362 

171.110 

171.860 

172.609 

173.360 

174.112 

174.866 

175.620 

176.360 


158.248 

158.975 

159.827 

160.618 

161.412 

162.206 

163.003 

163.800 

164.597 

165.384 

160.197 

166.999 

167.803 

168.610 

169.415' 

170.221 

171.030 

171.842 

172. G51 

173.448 

174.279 

175.093 

175.909 

176.728! 

177..546 

178.367 

179.1SS 

180.009 

180.833 

181.638 

182.485 

183.312 

184.142 

134.973 

185.803 

186.637 

187.470 

188.306 

189.142 

189.963 

190.818 

191.658 

192.499 

193.343 

194.185 

195.0.30 

195.876 

196.724 

197.573 

198.405 


3.51 
3.53 
3.53 
3.54 
3.55 
3.56 
3.57 
3.58 
3.59 

s.eo 

3.61 
3.63 

3.6a 

3.6* 

S.6S 

3.6«; 

3.GV 
3.R8 
3.C9 
3.70 
3.71 
3.73 
3>7^ 
3.74 
3.75 
3.76 
S.77 
3.78 
3.79 
3.80 
3.81 
3.83 
S.8S 
3.84 
3.85 
3.86 
3.87 
3.88 
3.89 
3.90 
3.91 
3.93 
3.93 
3.9* 
3.93 
3.96 
3.97 
3.98 
3.99 
4.0« 


177.1.30 

177.888 

178.648: 

179.407i 

180.1671 

180.930] 

181.691 

182.4561 

183.222, 

183.968' 

184.7.54  > 

185.522: 

186.292] 

187.0G2 

187.833 

18S.606 

189.378, 

190.154 

190.930 

191.688' 

192.485, 

193.263' 

194.042 

194.822 

195.604 

190.388, 

167.171 

197.958 

198.742 

199.512 

200.31S 

201.106 

201.8981 

202.6881 

203.480: 

204.272 

205.070, 

205.864 

206.662 

207.440 

208.256 

209.298 

209.856 

210.658 

211.462 

212.264 

213.070 

213.874 

214.C80 

215.464 


199.270 
200.1241 
200.979 
201.833 
202.688 
203.546 
204.403 
205.263 
206.]  24 
206.964' 
207.8491 
208.712i 
209.579  i 
210.445] 
211.312! 
212.182] 
2I3.05il 
213.9241 
214.797; 
215.649! 
216.5451 
217.4211 
218.297; 
219.175' 
220.055' 
220.937 
221.818 
222.702 
223.584 
22^^.451 
225.357 
220.245 
227.357 
228.024 
228.915 
229.806 
230.703 
231.597 
232.494 
!233.370i 
234.2881 
235.461 
236.088; 
236.991 
237.894 
238.797 
239.703 
240.609 
241.515 
,242.397 


4.01 

4.93 
4.03 
4.G4 
4.95 
4.06 
4.07 
4.«8 
4.09 
4.1« 
4.11 
4.13 
4.13 
4.1i 
4.15 
4.16 
4.17 
4.18 
4.19 
4.3« 
4.31 
4.33 
4.'2I.1! 
4.3i 
4.3S 
4.38 
4.37 
4.28 
4.39 
4.36 
4.31 
4.33 
4.33 
4.34 
4.35 
4.1(6 
4.37 
4.38 
4.39 
4.4« 
4.41 
4.43 
4.43 
4.44 
4.45 
4,4R 
4.47 
4.48 
4.49 
4.50 


243.333 
244.245 
24  3.147 
246.C70 
246. OSS 
247.900 
248.815 
249.733 
250.624 
251.. 550 
252.444 
253.415 
254.340 
255.263 
256.183 
2.57.115 
2.58.043 
'258.970 
1259.899 
I26O.8O2 
261.763 
202.697 
263.6.30 
264.500 
265.503 
266.439 
267.370 
268.313 
209.2C0 
270.171 
271.140 
272.0!;l 
273.037 
273.982 
274.91:7 
275.878 
276.827 
277.779 
278.730 
279.657 
280.630 
2^i..5t.O 
282.. 54  9 
2S3.5()u 
2S4.4G3 
285.421 
286.382 
287..345 
288.306 
289.242 


38 


MEASUREMENT   OF  IRRIGATION   WATER. 


Table  3 — Coefficients  C  to  be  applied  to  a  discharge  taken  from 
Table  l  or  2  for  a  head,  H,  to  obtain  the  discharge  of  the 
same  weir  zvhen  a  velocity  of  approach,  v,  exists;  computed 


Q'       Dl 

from    the   formula,   C   =   ■ —  =  — - 

Q      H\ 

and  20.) 


(See   paragraphs   13 


h 

h' 

H 

V 

0.2 

0.4 

0.6 

0.8 

1.0 

1.5   2.0  2.5  3.0 

3.5 

4.0 

5.0 

0.4 

0.0025 

0.0002 

1.014 

1.007  1.004  1.004 

1.004  1.002  1.002 

1 

1.0021.001 

1.001 

1.001 

1.001 

0.5 

.0039 

.0003 

1.027 

1.013  1.009^1.006 

1.006  1.004  1.003 

1.002  1.002 

1.002 

1.001 

1.001 

0.6 

.0056 

.0005 

1.037 

1.019  1.013  1.009 

1.008  1.005  1.004 

1.003  1.003 

1.002 

1.002 

1.C02 

0.7 

.0076 

.0007 

1.050 

1.026  1.017 

1.013 

1.011 

1.007  1.006 

1.004 

1.004 

1.003 

1.003 

1.002 

0.8 

.0099 

.0010 

1.064 

1.033  1.022 

1.016 

1.014 

1.009  1.007 

1.006  1.005 

1.004 

1.003 

1.003 

0.9 

.0126 

.0014 

1.082 

1.042  1.029 

1.021 

1.018 

1.012  1.009 

1.007  1.006 

1.005 

1.005 

1.004 

1.0 

.0155 

.0019 

1.098 

1.051  1.034 

1.027  1.022 

l.OloJl.Oll 

1.009  1.007 

1.006 

1.005 

1.005 

1.1 

.0188 

.0025 

1.122 

1.062  1.041 

1.031 

1.02611.017  1.013 

l.Olli  1.009 

1.008 

1.007 

1.006 

1.2 

.0224 

.0033 

1.141 

1.072  1.049  1.037 

1 

1.031  1.021  1.016 

1.013  1.011 

1.009 

1.008 

1.007 

1.3 

.0263 

.0041 

1.163 

1.084  1.057|  1.043 

1.036  1.024  1.018 

1.015  1.012 

1.011 

1.009 

1.008 

1.4 

.0305 

.0051 

1.1S6 

1.096  1.066  l.OoO;  1.041 

1.028  1.021 

1.017  1.014 

1.012 

1.011 

1.010 

1.5 

.0350 

.0064 

1.208 

1.109  1.075 

1.057 

1.047 

1.032  1.024 

1.019  1.016 

1.014 

1.012 

1.011 

1.6 

.0398 

.0079 

1.225 

1.122  1.084 

1.065 

1.052 

1.035  1.027 

1.022' 1.018 

1.016 

1.014 

1.012 

1.7 

.0449 

.0095 

1.254 

1.135  1.09311.071 

1.059!  1.040  1.031 

1.025  1.021 

1.018 

1.016 

1.014 

1.8 

.0504 

.0111 

1.277 

1.149  1.104 

l.OSO 

I.O65I  1.045  1.034 

1.027  1.023 

1 

1.020 

1.017 

1.016 

1.9 

.0561 

.0132 

1.308 

1.165  1.115 

1.089 

1.072  1.049  1.038 

1.030  1.026 

1.022 

1.019 

1.017 

2.0 

.0622 

.01.54 

1.335 

1.181  1.126 

1.097 

1.079  1.055' 1.042 

1.0.34  1.028 

1.025 

1.021 

1.019 

2.1 

.0686 

.0179 

1.363 

1.197  1.137 

1.106 

1.087 1 1.060^  1.046 

1.037  1.031 

1.027 

1.024 

1.021 

2.2 

.0752 

.0206 

1.391 

1.213  1.149 

1.118 

1.094 

1.065 

1.050 

1.039  1.034 

1.029 

1.026 

1.023 

2.3 

.0822 

.0235 

1.420 

1.231  1.161 

1.124 

1.102 

1.071 

1.054 

1.044  1.037  1.032 

1.02s 

1.025 

2.4 

.0895 

.0268 

1.449 

1.248  1.176 

1.134 

l.llOj  1.077  1.059 

1.047  1.040  1.034 

1.030 

1.027 

2.5 

.0972 

.0303 

1.480 

1.266  1.187 

1.145 

1.119  1.083  1.063 

1.051  1.043  1.037 

1.033 

1.02!) 

2.6 

.1051 

.0340 

1.511 

1.285  1.200 

1.155 

1.128  1.088  1.068 

1.055  1.046 

1.040 

1.035 

1.032 

2.7 

.1133 

.0381 

1.542 

1.303  1.213  1.166 

1.1371.095  1.073 

1.059  1.050 

1.043 

1.038 

1.034 

2.8 

.1219 

.0426 

1.573 

1.322  1.228  1.178 

1.1461 1.100|  1.078 

I.O63' 1.053 

1.046 

1.041 

1.036 

2.9 

.1307 

.0472 

1.606 

1.341  1.242:1.189 

1.153^1.108 

1.083  1.067  1.057 

1.049 

1.043 

1.039 

3.0 

0.1399 

0.0524 

1.637 

1.361  1.256  1.199 

1.165  1.115 

1.088  1.07211.061 

1.053 

1.046 

1.041 

MEASUREMENT   OF    IRRIGATION    WATER. 


39 


Table  4 — Coefficients  C''  to  he  applied  to  a  discharge  given  byTable  1 
or  2  for  a  head  H  to  give  discharge  of  same  weir  submerged. 


computed  front  the  formula  C  = = 

Q 

graphs  14  and  21.) 


Qi        {nH)\ 


H\ 


{Sec  para- 


d-h  H 

0.00 

0.01 

0.03 

0.03 

0.04 

0.05 

0.06 

0.07 

0.08 

0.09 

Tenths 

te 

0.0 

1.000 

1.006 

1.009 

1.009 

1.011 

1.011 

1.011 

1.009 

1.009 

1.007 

.1 

1.007 

l.OOo 

1.003 

1.000 

.997 

.994 

.991 

.988 

.983 

.981 

.2 

.078 

.973 

.970 

.966 

.963 

.958 

.955 

.951 

.946 

.942 

.3 

.939 

.9"5 

.931 

.926 

.921 

.917 

.913 

.909 

.903 

.900 

.4 

.895 

.891 

.885 

.881 

.875 

.871 

.865 

.859 

.854 

.848 

.5 

.842 

.837 

.831 

.825 

.819 

.812 

.806 

.799 

.792 

.785 

.6 

.778 

.771 

.764 

.756 

.748 

.740 

.733 

.724 

.715 

.707 

.7 

.698 

.689 

.680 

.670 

.660 

.649 

.639 

.626 

.615 

.603 

.8 

.589 

.576 

.562 

.547 

.531 

.517 

.501 

.486 

.469 

.453 

6.9 

.435 

.416 

.396 

.375 

.351 

.323 

.293 

.255 

.209 

.144 

,• 

40 


MEASUREMENT   OF   IRRIGATION    WATER. 


Tatle   5 — Acre-fcct  equivalent   to  a  given   number  of  second-feet 
flowing  for  a  given  length  of  time.     (See  paragraph  22.) 


' 

Hours 

Minutfs 

Second- 

feet 

f 

15 

30 

45 

1 

2 

3 

i 

5 

6 

0.01 

0.00021 

0.00041 

0.00062 

0.00083 

0.00165 

0.00248 

0.00,331 

0.00413 

0.00496 

.oqi 

.000!  1 

.00083 

.00124 

.00105 

.00331 

.00S96 

.00661 

.00826 

.00992 

.03 

.000(52 

.00124 

.00186 

.00248 

.00496 

.00744 

.00992 

.01240 

.01488 

.04 

.00083 

.00165 

.00248 

.00331 

.00651 

.00992 

.01322 

.01653 

.019.83 

.05 

.00103 

.00207 

.00310 

.00413 

.00826 

.01240 

.010.53 

.02066 

.02479 

.06 

.00124 
.00145 

.00248 
.00289 

.00372 
.00434 

.00496 

.00992 

.01488 
.01735 

.01983 
.02314 

.02179 
.02893 

.02975 

.07 

.00579 

.01157 

.03471 

.08 

.OOlfio 

.00331 

.00496 

.00061 

.01322 

.019,83 

.02045 

.03306 

.03967 

.09 

.00186 

.00372 

.00558 

.00744 

.01488 

.02231 

.02975 

.03719 

.04463 

.10 

.00207 

.00113 

.00020 

.00826 

.01653 

.02479 

.03306 

.04132 

.04959 

.11 

.00227 

.00455 

.00682 

.00909 

.01818 

.02727 

.03636 

.04545 

.05455 

.li 

.00248 

.00496 

.00744 

.00992 

.01983 

.02975 

.03967 

.04959 

.05950 

.13 

.00269 

.00537 

.00806 

.01074 

.02149 

.03223 

.04297 

.05372 

.06446 

.14 

.002S9 

.00579 

.00808 

.01157 

.02314 

.0.3471 

.04628 

.05785 

.06942 

.15 

.00310 

.00'.20 

.00930 

.01240 

.02479 

.0.3719 

.04959 

.06198 

.07438 

.16 

.00331 

.00061 

.00992 

.0132? 

.02545 

.03967 

.05289 

.06611 

.07934 

.17 

.00351 

.00702 

.01054 

.01405 

.02810 

.04215 

.05620 

.07025 

.08430 

.18 

.00372 

.00744 

.01116 

.01488 

.02975 

.04463 

.05950 

.07438 

.08926 

.19 

.00393 

.00785 

.01178 

.01,570 

.03140 

.04711 

.06281 

.07851 

.09121 

.20 

.001 !  3 

.0032') 

.01240 

.01653 

.03306 

.04959 

.06611 

.08264 

.09917 

.21 

.00434 

.00S6S 

.01302 

.01735 

.03471 

.05207 

.06942 

.08678 

.10413 

.23 

.00155 

.00909 

.01364 

.01818 

.03336 

.05455 

.07273 

.09091 

.10909 

.23 

.00475 

.009,50 

.01426 

.01901 

.03802 

.05702 

.07603 

.09504 

.11405 

.24 

.00^06 

.00992 

.01488 

.01983 

.03907 

.05950 

.07934 

.09917 

.11901 

.25 

.00517 

.01033 

.015.50 

.02066 

.04132 

.06198 

.08264 

.10331 

.12397 

.26 

.00537 

.01074 

.01611 

.02149 

.04297 

.06446 

.08595 

.10744 

.12893 

.27 

.00558 

.01116 

.01673 

.02231 

.04403 

.06694 

.08926 

.11157 

.13388 

.28 

.00579 

.01157 

.01735 

.02314 

.0i628 

.06942 

.09256 

.11570 

.13884 

.29 

.00599 

.01198 

.01797 

.02397 

.04793 

.07190 

.09587 

.11983 

.14380 

.30 

.00620 

.01240 

.018.59 

.02479 

.049.59 

.07438 

.09917 

.12397 

.14876 

.31 

.00640 

.01281 

.01921 

.02562 

.05124 

.07686 

.10248 

.12810 

.15372 

.32 

.00661 

.01322 

.01983 

.02645 

.05289 

.079.34 

.10579 

.13223 

.15868 

.33 

.00682 

.01364 

.02045 

.02727 

.05455 

.08182 

.10909 

.13636 

.16364 

.34 

.00702 

.01405 

.02107 

.02810 

.05620 

.08430 

.11240 

.14049 

.16859 

.35 

.00723 

.01446 

.02169 

.02893 

.05785 

.08678 

.11670 

.14403 

.17355 

.36 

.00744 

.01488 

.02231 

.02975 

.05950 

.08926 

.11901 

.14876 

.17851 

.37 

.00764 

.01529 

.02293 

.03058 

.06116 

.09173 

.12231 

.15289 

.18347 

.38 

.00785 

.01570 

.02355 

.03140 

.06281 

.09421 

.12562 

.15702 

.18843 

.39 

.00806 

.01611 

.02417 

.03223 

.06446 

.09669 

.12893 

.16116 

t 19339 

.40 

.00S26 

.01653 

.02479 

.03306 

.06611 

.09917 

.13223 

.16529 

.19835 

.41 

.00847 

.01694 

.02541 

.03388 

.06777 

.10165 

.13554 

.16942 

.20331 

.42 

.00868 

.01735 

.02603 

.03471 

.06942 

.10413 

.13884 

.17355 

.20826 

.43 

.00888 

.01777 

.02665 

.03554 

.07107 

.10661 

.14215 

.17769 

.21.322 

.44 

.00909 

.01818 

.02727 

.03636 

.07273 

.10909 

.14545 

.18182 

.21818 

.45 

.00930 

.01859 

.02789 

.03719 

.07438 

.11157 

.14876 

.18595 

.22314 

.46 

.00950 

.01901 

.02851 

.03802 

.07003 

.11405 

.15207 

.19008 

.22810 

.47 

.00971 

.01942 

.02913 

.03884 

.07769 

.116.53 

.15537 

.19421 

.23306 

AH 

.00992 

.01983 

.02975 

.03967 

.079.34 

.11901 

.15868 

.19835 

.23802 

.49 

.01012 

.02025 

.03037 

.04049 

.0,8099 

.12149 

.16198 

.20248 

.24297 

0.50 

0.01033 

0.02066 

0.03099 

0.04132 

0.08264 

0.12397 

0.16529 

0.20661 

0.24793 

MEASUREMENT   OF   IRRIGATION   WATER. 


41: 


Table   5 — Acrc-fcet  equivalent   to   a  given   number   of  second-feet 
flowing  for  a  given  length  of  time.     {See  paragraph  22.) 


Second- 

Minutes 

Hours 

feet 

15 

30 

45 

1 

2 

3 

4 

5 

6 

0.51 

0.01054 

0.02107 

0.03161 

0.04215 

0.08430 

0.12645 

0.16859 

0.21074 

0.25289 

.52 

.01074 

.02149 

.03223 

.04297 

.08595 

.12893 

.17190 

.21488 

.25785 

.53 

.01095 

.02190 

.03285 

.04380 

.08760 

.13140 

.17521 

.21901 

.26281 

.54 

.01116 

.02231 

.03347 

.04463 

.08926 

.13388 

.17851 

.22314 

.26777 

.65 

.01136 

.02273 

.03409 

.04545 

.09091 

.13636 

.18182 

.22727 

.27273 

.56 

.01157 

.02314 

.03471 

.04628 

.09256 

.13884 

.18512 

.23140 

.27769 

.67 

.01178 

.02355 

.03533 

.04711 

.09421 

.14132 

.18843 

.23554 

.28264 

.58 

.01108 

.02397 

.03595 

.04793 

.09587 

.14380 

.19173 

.23967 

.28760 

.59 

.01219 

.02438 

.03657 

.04876 

.09752 

.14628 

.19504 

.24380 

.29256 

.60 

.01240 

.02479 

.03719 

.04959 

.09917 

.14876 

.19835 

.24793 

.29752 

.61 

.01260 

.02521 

.03781 

.05041 

.10083 

.15124 

.20165 

.25207 

.30248 

.68 

.01281 

.02562 

.03843 

.05124 

.10248 

.15372 

.20496 

.25620 

.30744 

.63 

.01302 

.02603 

.03905 

.05207 

.10413 

.15620 

.20826 

.26033 

.31240 

.M 

.01322 

.02645 

.03967 

.05289 

.10579 

.15868 

.21157 

.26446 

,31735 

.65 

.01343 

.02686 

.04029 

.05372 

.10744 

.16116 

.21488 

.26859 

.32231 

.66 

.01364 

.02727 

.04091 

.05455 

.10909 

.10364 

.21818 

.27273 

.32727 

.67 

.01384 

.02769 

.04153 

.05537 

.11074 

.16611 

.22149 

.27686 

.33223 

.68 

.01405 

.02810 

.04215 

.05020 

.11240 

.16859 

.22479 

.28099 

.33719 

.69 

.01426 

.02851 

.04277 

.05702 

.11405 

.17107 

.22810 

.28512 

.34215 

.70 

.01446 

.02893 

.04339 

.05785 

.11570 

.17355 

.23140 

.28926 

.34711 

.71 

.01467 

.02934 

.04401 

.05S68 

.11735 

.17603 

.23478 

.29339 

.35207 

.72 

.01488 

.02975 

.04463 

.05950 

.11901 

.17851 

.23802 

.29752 

.35702 

.73 

.01508 

.03017 

.04525 

.06033 

.12066 

.18099 

.24132 

.30165 

.36198 

.74 

.01529 

.03058 

.04587 

.06116 

.12231 

.18347 

.24463 

.30579 

.36694 

.75 

.01550 

.03099 

.04049 

.06198 

.12397 

.18595 

.24793 

.30992 

.37190 

.76 

.01570 

.03140 

.04711 

.06281 

.12562 

.18843 

.25124 

.31405 

.37685 

.77 

.01591 

.03182 

.04773 

.06364 

.12727 

.19091 

•  .25455 

.31818 

.38182 

.78 

.01611 

.03223 

.04835 

.06446 

.12893 

.193.39 

.25785 

.32231 

.38678 

.79 

.01632 

.03264 

.04897 

.06529 

.13058 

.19587 

.26116 

.32645 

.39173 

.89 

.016.53 

.03306 

.04959 

.06611 

.13223 

.19835 

.26446 

.33058 

.39669 

.81 

.01673 

.03347 

.05021 

.03694 

.13388 

.20083 

.26777 

.33471 

.40165 

.82 

.01694 

.03388 

.05083 

.06777 

.13554 

.20331 

.27107 

.33884 

.40661 

.83 

.01715 

.03430 

.05145 

.06359 

.13719 

.20579 

.27438 

.34297 

.41157 

.84 

.01735 

.03471 

.05207 

.06942 

.13884 

.20826 

.27769 

.34711 

.41653 

.85 

.01756 

.03512 

.05269 

.07025 

.14049 

.21074 

.28099 

.35124 

.42149 

.86 

.01777 

.03554 

.05331 

.07107 

.14215 

.21322 

.28430 

.35537 

.42645 

.87 

.01797 

.03595 

.05393 

.07190 

.14380 

.21570 

.28760 

.35950 

.43140 

.88 

.v;l81S 

.03636 

.05455 

.07273 

.14.545 

.21818 

.29091 

.36364 

.43636 

.89 

.01839 

.03678 

.05517 

.07355 

.14711 

.22066 

.29421 

.36777 

.44132 

.90 

.01859 

.03719 

.05579 

.07438 

.14876 

.22314 

.29752 

.37190 

.44628 

.91 

.01880 

.03760 

.05640 

.07521 

.15041 

.22562 

.30083 

.37603 

.45124 

.92 

.01901 

.03802 

.03702 

.07603 

..15207 

.22810 

..30413 

.38017 

.45620 

.93 

.01921 

.03843 

.05764 

.07686 

.15.372 

.23058 

.30744 

.38430 

.46116 

.94 

.01942 

.03884 

.05826 

.07769 

.15537 

.23306 

.31074 

.38843 

.46611 

.95 

.01903 

.03926 

.05888 

.07851 

.15702 

.23554 

.31405 

.39256 

.47107 

.96 

.01983 

.03967 

.05950 

.07934 

.15868 

.23802 

.31735 

.39669 

.47603 

.97 

.02004 

.04008 

.06012 

.08017 

.16033 

.24049 

.32066 

.40083 

.48099 

.98 

.02025 

.04049 

.06074 

.08099 

.16198 

.24297 

.32397 

.40496 

.48515 

.99 

.02045 

.04091 

.06138 

.08182 

.16364 

.24545 

.32727 

.40909 

.49091 

1.00 

0.0206G 

0.04132 

0.06198 

0.08264 

0.16529 

0.24793 

0.33058 

0.41322 

0.49587 

42 


MEASUREMENT   OF   IRRIGATION   WATER. 


Table   5 — Acre-feet   equivalent   to   a   given   number  of  cecond-feet 
flowing  for  a  given  length  of  time.     (See  paragraph  22.) 


Hours 


10 


11 


12 

13 

14 

15 


0.00579  0 
.01157 
.01735 
.02314 
.02893 
.03471 
.04049 
.04028 
.nr,2()7 
.0.3785 
.00304 
.00942 
.07521 
.080991 
.08078 
.09256' 
.09835; 
.104131 
.10992! 
.11570 
.12149] 
.12727 
.133061 
.138841 
.14463 
.15041 
.15020 
.16198 
.16777! 
.17355! 
.17934' 
.18512! 
.19091! 
.19069! 
.202481 
.20826 1 
.21405 
.219831 
.22562! 
.23140! 
.23719! 
.24297; 
.24876! 
.25455, 
.26033; 
.266111 
.27190] 
.27709 
.283471 

0.28926,0, 


.00661 
.01322 
.01983 
.02045 
.03306 
.03967 
.04028 
.05289 
.05950 
.00011 
.07273 
.07934 
.Oj;595 
.09256 
.09917 
.10579 
.11240 
.11901 
.12562 
.13223 
.13884 
,14545 
,15207 
,15808 
,10529 
,17190 
,17851 
.18512 
,19173 
,19835 
.20496 
.21157 
,21818 
.22479 
,23140 
,23802 
.24463 
.25124 
,25785 
.26446 
.27107 
,27769 
.28430 
.29091 
.29752 
.30413 
.31074 
.31735 
.32397 
33058 


0.00744 
.01488 
.02231 
.02975 
.03719 
.04463 
.05207 
.05950 
.06694 
.07438 
.08182 
.08926 
.09669 
.10413 
.11157 
.11901 
.12645 
.13388 
.14132 
.14876 
.15620 
.16304 
.17107 
.17851 
.18595 
.19339 
.20083 
.20826 
.21570 
.22314 
.2.50.58 
.23802 
.24545 
.25289 
.26033 
.20777 
.27521 
.28264 
.29008 
.29752 
.30496 
.31240 
.31983 
.32727 
.33471 
.34215 
.34959 
.35702 
.36446 
.37190 


0.00826 
.01653 
.02479 
.03306 
.04 132 
.04959 
.05785 
.OoOll 
.07438 
.0S264 
.09091 
.09917 
.10744 
.11570 
.12397 
.13223 
.14049 
.14870 
.15702 
.16529 
.17355 
.18182 
.19008 
.19835 
.206611 
.21488 
.223141 
.23140 
.23907 
.24793 
.25620 
.26446 
.27273 
.28099 
.28926 
.29752 
.30579 
.31405 
.32231 
.33058 
.33884 
.34711 
.35537 
.36364 
.37190 
.38017 
.38843 
.39669 
.40496 

0.41322 


0.00909 

■ 
0.00992 

0.01074 

0.01157 

.01818 

.01983 

.02149 

.02314 

.02727 

.02975 

.03223 

.03471 

.03636 

.03967 

.04297 

.04628 

.04545 

.04959 

.05372 

.05785 

.0.5455 

.05950 

.06446 

.06942 

.0ti304 

.06942 

.07521 

.08099 

.07273 

.07934 

.08595 

.09250 

.08182 

.08926 

.09669 

.10413 

.09091 

.09917 

.10744 

.11570 

.10000 

.10909 

.11818 

.12727 

.10909 

.11901 

.12893 

.13884 

.11818 

.12893 

.13967 

.15041 

.12727 

.13884 

.15041 

.16198 

.13636 

.14876 

.10116 

.17355 

.14545 

.15868 

.17190 

.18512 

.15455 

.16859 

.18264 

.19369 

.16364 

.17851 

.19339 

.20826 

.17273 

.18843 

.20413 

.21983 

.18182 

.19835 

.21488 

.23140 

.19091 

.20826 

.22562 

.24297 

.20000 

.21818 

.23636 

.25455 

.20909 

.22810 

.24711 

.26611 

.21818 

.23802 

.25785 

.27769 

.22727 

.24793 

.268.59 

.28926 

.23636 

.2,5785 

.27934 

.30083 

.24.545 

.26777 

.29008 

.31240 

.25455 

.27769 

.30083 

.32397 

.26364 

.28760 

.31157 

.33554 

.27273 

.29752 

.32231 

.34711 

.28182 

.  .30744 

.33300 

.35868 

.29091 

.31735 

.34380 

.37025 

.30000 

.32727 

.35155 

.38182 

.30909 

..33719 

.30529 

.39339 

.31818 

.34711 

.37003 

.40496 

.32727 

.35702 

.38678 

.41653 

.33636 

.36694 

.39752 

.42810 

.34545 

.37686 

.40826 

.43967 

.35455 

.38678 

.41901 

.45124 

.36304 

.39669 

.42975 

.46281 

.37273 

.40661 

.44049 

.47438 

.38182 

.41653 

.45124 

.48595 

.39091 

.42645 

.46198 

.49752 

.40000 

.43636 

.47273 

.50909 

.40909 

.44628 

.48347 

.52006 

.41818 

.45020 

.49421 

.53223 

.42727 

.46011 

.50496 

.54380 

.43636 

.47603 

.51570 

.5.5537 

.44545 

.48595 

.52045 

.56694 

0.45455 

0.49587 

0.53719 

0.57851 

0.0124C 
.02479 
.03719 
.04959 
.06198 
.07438 
.08678 
.09917 
.11157 
.12397 
.1363P 
.14£76 
.16116 
.17355 
.18595 
.19835 
.21074 
.22314 
.23554 
.24793 
.26033 
.27273 
.28512 
.29752 
.30992 
.32231 
.33471 
.34711 
.35950 
.37190 
.38430 
.39669 
.40909 
.42149 
.43388 
.44628 
.45868 
.47107 
.48347 
.49587 
.50826 
.52066 
.53306 
.54545 
.55785 
.57025 
.58264 
.59504 
.60744 

0.61983 


MEASUREMENT   OF   IRRIGATION    WATER. 


43 


Table   5 Acre-fcct  equivalent   to   a  given  number  of  second-feet 

flowing  for  a  given  length  of  time.     (See  paragraph  22.) 


Hours 

Second- 

feet 

7 

8 

9 

10 

11 

12 

13 

14 

15 

0.51 

0.29504 

0.33719  0.37934!0.42149 

0.46304 

0.50579 

0.54793 

0.59008 

0.63223 

.S2 

.30083 

.34380 

.38678 

.42975 

.47273 

.51570 

.55868 

.60165 

.64463 

.53 

.30661 

.35041 

.39421 

.43802 

.48182 

.52562 

.50942 

.61322 

.65702 

.54 

.31240 

.35702 

.40165 

.44628 

.49091 

.53554 

.58017 

.62479 

.66942 

.55 

.31818 

.30364 

.40909 

.45455 

.50000 

.54545 

.59091 

.63636 

.68182 

.56 

.32397 

.37025 

.41653 

.46281 

.50909 

.55537 

.60165 

.64793 

.69421 

.67 

.32975 

.37686 

.42397 

.47107 

.51818 

.56529 

.61240 

.65950 

.70661 

.58 

.33554 

.38347 

.43140 

.47934 

.52727 

.57521 

.62314 

.67107 

.71901 

.59 

.34152 

.39008 

.43884 

.48760 

.53636 

.58512 

.63388 

.68264 

.73140 

.GO 

.34711 

.39669 

.44628 

.49587 

.54.545 

.59504 

.64463 

.69421 

.74380 

.61 

.35289 

.40331 

.45372 

.50413 

.55455 

.60496 

.65537 

.70579 

.75620 

.62 

.35868 

.40992!  .46116 

.51240 

.56364 

.61488 

.66611 

.71735 

.76859 

.63 

.36446 

.41653 

.46859 

.52066 

.57273 

.62479 

.67686 

.72893 

.78099 

.64 

.37025 

.42314 

.47603 

.52893 

.58182 

.63471 

.68760 

.74049 

.79339 

.65 

.37603 

.42975 

.48347 

.53719 

.59091 

.64463 

.69835 

.75207 

.80579 

.66 

.38182 

.43636 

.49091 

.54545 

.60000 

.65455 

.70909 

.76364 

.81818 

.67 

.38760 

.44297 

.49835 

.55372 

.60909 

.66446 

.71983 

.77521 

.83058 

.6S 

.39339 

.44959 

.50579 

.58198 

.61818 

.67438 

.73058 

.78678 

.84297 

.69 

.39917 

.45620 

.51322 

.57025 

.62727 

.68430 

.74132 

.79835 

.85537 

.70 

.40496 

.46281 

.52066 

.57851 

.63636 

.69421 

.75207 

.80992 

.86777 

.71 

.41074 

.46942 

.52810 

.58678 

.64.545 

.70413 

.76281 

.82149 

.88017 

.72 

.41653 

.47603 

.53554 

.59504 

.65455 

.71405 

.77355 

.83306 

.89256 

.73 

.42231 

.48264 

.54297 

.60331 

.66364 

.72397 

.78430 

.84463 

.90496 

.74 

.42810 

.48926 

.55041 

.61157 

.67273 

.73388 

.79504 

.85620 

.91735 

.75 

.43388 

.49587 

.55785 

.61983 

.68182 

.74380 

.80579 

.86777 

.92975 

.76 

.43967 

.50248 

.56529 

.62810 

.69091 

.75372 

.81653 

.87934 

.94215 

.77 

.44545 

.50909 

.57273 

.63636 

.70000 

.76364 

.82727 

.89091 

.95455 

.78 

.45124 

.51570 

.58017 

.64463 

.70909 

.77355 

.83802 

.90248 

.96694 

.79 

.45702 

.52231 

.58760 

.65289 

.71818 

.78347 

.84876 

.91405 

.97934 

.80 

.46281 

.52893 

.59504 

.66116 

.72727 

.79339 

.85950 

.92562 

.99173 

.81 

.46859 

.53534 

.60248 

.66942 

.73636 

.80331 

.87025 

.93719 

1.00413 

.82 

.47438 

.54215 

.60992 

.67769 

.74545 

.81322 

.88099 

.94876 

1.01653 

.83 

.48017 

..54876 

.61735 

.68595 

.75455 

.82314 

.89173 

.96033 

1.02893 

.84 

.48595 

.55537 

.62479 

.69421 

.76364 

.83306 

.90248 

.97190 

1.04132 

.85 

.49173 

.56198 

.63223 

.70248 

.77273 

.84297 

.91322 

.98347 

1.05372 

.86 

.49752 

.56859 

.63967 

.71074 

.78182 

.85289 

.92397 

.99504 

1.060U 

.87 

.50331 

..57521 

.64711 

.71901 

.79091 

.86281 

.93471 

1.00661 

1.07851 

.88 

.50909 

.58182 

.05455 

.72727 

.80000 

.87273 

.94545 

1.01818 

1.09091 

.89 

.51488 

.58843 

.66198 

.73554 

.80909 

.88264 

.95620 

1.02975 

1.10331 

.90 

.52066 

.59504 

.66942 

.74380 

.81818 

.89256 

.96694 

1.04132 

1.11570 

.91 

.52645 

.60165 

.67686 

.75207 

.82727 

.90248 

.97769 

1.05289 

1.12810 

.92 

.53223 

.60826 

.08430 

.76033 

.83636 

.91240 

.98843 

1.06446 

1.14049 

.93 

.53802 

.61488 

.69173 

.76859 

.84545 

.92231 

.99917 

1.07603 

1.15289 

.94 

.54380 

.62149 

.69917 

.77686 

.85455 

.93223 

1.00992 

1.08760 

1.16529 

.95 

.54959 

.62810 

.70661 

.78512 

.86364 

.94215 

1.02066 

1.09917 

1.17769 

.96 

.55537 

.63471 

.71405 

.79339 

.87273 

.95207 

1.03140 

1.11074 

1.19008 

.97 

.56116 

.64132 

.72149 

.80165 

.88182 

.96198 

1.04215 

1.12231 

1.20248 

.98 

.56694 

.64793 

.72893 

.80992 

.89091 

.97190 

1.0.5289 

1.13388 

1.21488 

.99 

.57273 

.65455 

.73636 

.81818 

.90000 

.98182 

1.06364 

1.14545 

1.22727 

1.00 

0.57851 

0.66116  0.74380 

0.82645 

0.90900 

0.99173 

1.07438 

1.15702 

1.23967 

44 


MEASUREMENT  OP   IRRIGATION   WATER. 


Table   5 — Acre-feet   equivalent   to   a   given    number  of  second-feel 
flowing  for  a  given  length  of  time.     {See  paragraph  22.) 


Hours 

Second- 

feet 

13 

17 

18 

19 

30 

31 

Ti 

33 

24 

0.01 

0.01322 

0.01405 

0.01488 

0.01570 

0.01053 

0.01735 

0.01818 

0.01901 

0.01983 

.02 

.02645 

.02810 

.02975 

.03140 

.03306 

.03471 

.03636 

.03802 

.03967 

.03 

.03907 

.04215 

.01463 

.04711 

.04959 

.05207 

.05455 

.05702 

.05950 

.04 

.05289 

.05620 

.05950 

.00281 

.00611 

.06942 

.07273 

.07603 

.07934 

.03 

.06611 

.07025 

.07438 

.07851 

.08264 

.08678 

.09091 

.09504 

.09917 

.06 

.079.34 

.08430 

.08926 

.00421 

.09917 

.10413 

.10909 

.11405 

.11901 

.07 

.09256 

.09835 

.10413 

.10992 

.11570 

.12149 

.12727 

.13.306 

.13884 

.08 

.10579 

.11240 

.11901 

.12562 

.13223 

.13884 

.14.545 

.1.5207 

.15868 

.09 

.11901 

.12645 

.13388 

.14132 

.14S76 

.15620 

.16364 

.17107 

.17851 

.10 

.13223 

.14049 

.14876 

.1.5702 

.16529 

.17355 

.18182 

.19008 

.19835 

.11 

.14545 

.154.55 

.16304 

.17273 

.18182 

.19091 

.20000 

.20909 

.21818 

.1« 

.15808 

.16859 

.17851 

.18843 

.19835 

.20826 

.21818 

.22810 

.23802 

.13 

.17190 

.18264 

.193.39 

.20413 

.21488 

.22562 

.23636 

.24711 

.25785 

.14 

.18512 

.19069 

.20S26 

.21983 

.23140 

.24297 

.2,5455 

.26611 

.27769 

.16 

.19835 

.21074 

.22314 

.23554 

.24793 

.26033 

.27273 

.28512 

.29752 

.16 

.21157 

.22479 

.23802 

.25124 

.26446 

.27769 

.29091 

.30413 

.31735 

.17 

.22479 

.23884 

.25289 

.20694 

.28099 

.29504 

.,30909 

.32314 

.33719 

.18 

.2.3802 

.25289 

.26777 

.28264 

.29752 

.31240 

.32727 

.34215 

.35702 

.10 

.25124 

.26694 

.28264 

.29835 

.31405 

.32975 

..34545 

.36116 

.37686 

.20 

.26446 

.28099 

.29752 

.31405 

.33058 

.34711 

.36364 

.38017 

.39669 

.31 

.27769 

.29.504 

.31240 

.32975 

.34711 

.36440 

.38182 

.39917 

.41653 

.23 

.29091 

.30909 

.32727 

.34.545 

.36364 

.38182 

,40000 

.41818 

.4.3636 

.23 

.30413 

.32314 

.34215 

..30116 

.38017 

.39917 

.41818 

.43719 

.45620 

.24 

.31735 

.33719 

.35702 

.37686 

.39069 

.41653 

.43636 

.45620 

.47603 

.25 

.33058 

.35124 

.37190 

.39256 

.41322 

.43388 

.45455 

.47521 

.49587 

.26 

.34380 

.30529 

.38078 

.40826 

.42975 

.45124 

.47273 

.49421 

.51570 

.37 

.35702 

.37934 

.40165 

.42397 

.44628 

.46859 

.49091 

.51322 

.53554 

.28 

.37025 

.39339 

.41653 

.43967 

.40281 

.48595 

.50909 

.53223 

.55537 

.2!) 

.38347 

.40744 

.43140 

.45537 

.47934 

.50331 

.52727 

.55124 

.57521 

.30 

.39669 

.42149 

.44628 

.47107 

.49587 

.52006 

.54545 

.57025 

.59504 

.31 

.40992 

.43554 

.40116 

.48078 

.51240 

.53802 

.56364 

.58926 

.61488 

.33 

.42314 

.44959 

.47603 

.50248 

.52893 

.55537 

.68182 

.60826 

.63471 

.33 

.43636 

.46364 

.49091 

.51818 

.54545 

.57273 

.60000 

.62727 

.65455 

.34 

.44959 

.47769 

.50579 

.53388 

.56198 

.59008 

.61818 

.04628 

.67438 

.35 

.46281 

.49173 

.52006 

.54959 

.57851 

.60744 

.63636 

.66529 

.69421 

.36 

.47603 

.50579 

.53554 

.56529 

.59504 

.62479 

.05455 

.681.30 

.71405 

.37 

.48926 

.51983 

.55041 

.58099 

.61157 

.64215 

.07273 

.70331 

.73388 

.38 

.50248 

.53388 

.50529 

.59069 

.62810 

.65950 

.69091 

.72231 

.75372 

.39 

.51.570 

.54793 

.58017 

.61240 

.64463 

.67686 

.70909 

.74132 

.77355 

.40 

.52893 

.56198 

.59,504 

.62810 

.60116 

.69421 

.72727 

.76033 

.79339 

.41 

.54215 

.57603 

.00992 

.64380 

.67769 

.71157 

.74545 

.77934 

.81322 

.43 

.55537 

.59008 

.62479 

.659.50 

.69421 

.72893 

.76364 

.79835 

.83306 

.43 

.56859 

.60413 

.63967 

.67.521 

.71074 

.74628 

.78182 

.81735 

.85289 

.44 

.58182 

.61818 

.654.55 

.60091 

.72727 

.76364 

.80000 

.83636 

.87273 

.45 

.59504 

.63223 

.60942 

.70061 

.74380 

.78099 

.81818 

.85537 

.89256 

.4« 

.60826 

.64628 

.(58430 

.72231 

.70033 

.79835 

.83036 

.874.38 

.91240 

.47 

.02149 

.60033 

.09917 

.73802 

.77086 

.81570 

.S5455 

.89339 

.93223 

.48 

.>i.3471 

.67438 

.71405 

.75372 

.79339 

.83306 

.87273 

.91240 

.95207 

.49 

.r.4793 

.68843 

.72893 

.70942 

.80992 

.8.5041 

..S9091 

.93140 

.97190 

0.50 

0.06116 

0.70248 

0.74380 

0.78512 

0.82645 

0.86777 

0.90909 

0.95041 

0.99173 

MEASUREMENT   OF   IRRIGATION    WATER. 


45 


Table   5 — Acre-feet  equivalent   to   a  given  number  of  secoiid-feet 
flowing  for  a  given  length  of  time.     (See  paragraph  32.) 


Hours 

Second- 

feet 

16 

17 

18 

19 

29 

21 

23 

23 

24 

0.51 

0.67438 

1      1 
0.71853  0.75868  0.800S3 

0.84297 

0.8S512 

0.92727 

0.96942 

1.011.57 

.53 

.6S7bO 

.73058  .77355 

.81653 

.85950 

.90248 

.94545 

.98843 

1.03140 

.53 

.700S3 

.74463  .78843 

.83223 

.87603 

.91983 

.96364 

1.00744 

1.05124 

.54 

.71405 

.75868  .80331 

.84793 

.89256 

.93719 

.98182 

1.02045i  1.07107 

.55 

.72727 

.77273  .81318 

.80364 

.90909 

.95455 

1.00000 

1.04545!  1.09091 

.56 

.740-i9 

.78078  .83306 

.87934 

.92562 

.97190 

1.01818 

1.00446  1.11074 

.57 

.75372 

.80083 

.84793 

.89504 

.94215 

.98926 

1.03636 

1.08347  1.13058 

.58 

.76694 

.81487 

.80281 

.91074 

.95868 

1.00661 

1.05455 

1.10248  1.15041 

.59 

.78017 

.82893 

.87769 

.92645 

.9752! 

1.02.397 

1.07273 

1.121491  1.17025 

.60 

.79339 

.84297 

.89256 

.91215 

.99173 

1.04132 

1.09091 

1.14049  1.19908 

.61 

.8006 1 

.85702 

.93744;  .95785 

1.00S26 

1.0586S 

1.10909 

1.15950  1.20992 

.63 

.S19S3 

.87107 

.922311  .97355 

1.02479 

1.07603 

1.12727 

1.178511  1.22975 

.63 

.83306 

.83512 

.937191  .9S926 

1.04132 

1.09339 

1.14545 

1.197.521  1.24959 

.64 

.84628 

.89917 

.9520711.00496 

1.05785 

1.11074 

1.16364 

1.21653!  1.26942 

.65 

.859o0 

.91.322  .9669411.02066 

1.07438 

1.12810 

1.18182 

1.23554!  1.2S926 

.66 

.87273 

.92727  .93  lS2i  1.03036 

1.09991 

1.14545 

1.20000 

1.25455|  1.30909 

.67 

.88595 

.94132  .90669]  1.05207 

1.10744 

1.16281 

1.21818 

1.27355;  1.32893 

.68 

.89917 

.9.553711.01157,1.06777 

1.12397 

1.18017 

1.23636 

1.29256 

1.. 34876 

.69 

.91240 

.96012]  1.02645J1.08347 

1.14049 

1.19752 

1.2.5455 

1.31157 

1.36859 

.70 

.92562 

.98347  1.04132  1.09917 

1.15702 

1.21487 

1.27273 

1.33058 

1.38843 

.71 

.93834 

.99752  1.05620  1.11483 

1.17355 

1.23223 

1.29091 

1.34959 

1.40S26 

.73 

.95207 

1.01157, 1.07107|1.13058 

1.19008 

1.24959 

1.30909 

1.36859 

1.42810 

.73 

.96529 

1.025671 1.08595  1.14628 

1.20661 

1.26694 

1.32727 

1.38760 

1.44793 

.74 

.97851 

1.03967il.l0083'l. 16198 

1.22314 

1.28430 

1.34545 

1.4000! 

1.46777 

.75 

.99173 

1.0537211. 11570il. 17769 

1.23967 

1.30165 

1.3C364 

1.42562!  1.48700 

.76 

1.00496 

1.0677711. 1305811. 19339 

1.25620 

1.31001 

1.3S1S2 

1.44463 

1.50744 

.77 

1.01818 

1.08182il.l4545il.20909 

1.27273 

1.33636 

1.40000 

1.40364 

1.52727 

.7S 

1.03140 

1.095S7|l.lG033jl.22479 

1.28926 

1.35372 

1.41818 

1.48204 

1.54711 

.78 

1.04463 

1. 10902a. i7521jl.24049 

1.30579 

1.37107 

1.43036 

1.501651  1.56094 

.80 

1.05785 

1.12397il.l9008i  1.2.5620 

1.32231 

1.38S43 

1.45455 

1.52066 

1.58678 

.81 

1.07107 

1.13892, 1.20490]!. 27190 

1.33SS4 

1.40579 

1.47273 

1.63967 

1.00001 

.83 

1.084.30 

1.15207]1.21983  1.28760 

1.35537 

1.42314 

1.49091 

1.55S6S 

1.C2645 

.83 

1.09752 

1.166U,1.23471]1.3033i 

1.37190 

1.44049 

1.50909 

1.57769 

1.64028 

.84 

1.11074 

1. 18017]!. 2495911.31901 

1.38843 

1.45785 

1.52727 

1.59670 

1.666!! 

.85 

1.12.397 

1.10421  1.20440]1.3347! 

1.40496 

1.47521 

1.54545 

1.61570 

1.68595 

.86 

1.13719 

1.20826  1.27934|1.3.W4! 

1.42149 

1.49256 

1.56364 

1.6347! 

1.70579 

.87 

1.15041 

1.22231,1.29421:1.36611 

1.43302 

1.50992 

1.58182 

1.653721  1.72502 

.88 

1.16364 

!. 23636]!. 30909;1.3S182 

1.45455 

1.52727 

1.60000 

1.67273  1.74515 

.89 

1.17686 

1.25041  1.32397  1.39752 

1.47107 

1.54463 

1.61818 

1.69173  1.76529 

.90 

1.1900S 

1.264-16  1.33884,1.41322 

1.48760 

1.56198 

1.63036 

1.71074  1.78512 

.91 

1.20331 

1.27851  1.. 3.5372 11.42893 

1.50413 

1.57934 

1.65155 

1.72975  1.80496 

.93 

1.21653 

1.29256  1.30859,1.44463 

1.52066 

1.59669 

1.67273 

1.74870 

1.82479 

.93 

1.22975 

1..3061U  1.. 38347  1.46033 

1.53719 

1.61405 

1.69091 

1.76777 

1.84463 

.94 

1.24297 

1.32066  1.39835  1.47603 

1.55372 

1.63140 

1.70909 

1.78678 

1.86446 

.95 

1.25620 

1.3347!  1.41322  1.49173 

1.57025 

1.64876 

1.72727 

1.8057S 

1.83430 

.96 

1.26942 

1.34  376  1.42810,1.50744 

1.58678 

1.66011 

1.74545 

1.82479 

1.90413 

.97 

1.28264 

1.36281  1.44297:1.52314 

1.60331 

1.68347 

1.76364 

1.84380 

1.92397 

.98 

1.29587 

1.37686,1.45785,1.53884 

1.61983 

1.70083 

1.78182 

1.86281 

1.94380 

.99 

1.30909 

1.39091 1 1.47273  i  1.55455 

1.63636 

1.71818 

1.80000 

1.88182 

1.96364 

1.00 

1.32231 

1.40496  1.48760 

1.57025 

1.65289 

1.73554 

1.81818 

1.90083 

1.98347 

46 


MEASUREMENT   OF  IRRIGATION   WATER. 


Tatle   5 — Acre-feet  equivalent   to   a  given  number  of  second-feet 
flowing  for  a  given  length  of  time.     {See  paragraph  22.) 


i 

Days  of  24  Hours 

Second- 
feet 

3 

3 

4 

5 

1 

7 

8 

9 

10 

0.01 

0.03967 

1 
0.05950  0.07934 

0.09917 

0.11901 

0.13884'  0.1586S 

0.17851  0.19835 

.02 

.07934 

.119U1|  .15868 

.19835 

.23S02 

.27769 

.31735 

.35702 

.39669 

.63 

.11901 

.178511  .23802 

.29752 

.35702 

.41653 

.47603 

.53554 

.59504 

.04 

.15868 

.2.3802  .31735 

.39669 

.47603 

.55537 

.63471 

.71405 

.793.39 

.05 

.19835 

.29752 

.39669 

.49.587 

.59504 

.69421 

.79339 

.89256 

.99173 

.06 

.23802 

.35702 

.47603 

.59504 

.71405 

.833061   .95207 

1.07107 

1.19008 

.07 

.27769 

.41653 

.55537 

.69421 

.83306 

.97190  >.  11074 

1.24959 

1.38842 

.08 

.31735 

.47603 

.63471 

.79339 

.95207 

1.11074  1.26942 

1.42810 

1.58678 

.09 

.35702 

.53554 

.71405 

.89256 

1.07107 

1.24959  1.42810 

1.60661 

1.78512 

.10 

.39669 

.59504 

.79339 

.99173 

1.19008 

1.38843  1.58678 

1.78512 

1.98347 

.11 

.43636 

.65455 

.87273 

1.09091 

1.30909 

1.527271  1.74.545 

1.96364 

2.18182 

.13 

.47603 

.71405 

.95207  1.19008 

1.42810 

1.68611  1.90413 

2  14215  2.38016 

.13 

.515701  .77355 

1.03140  1.28925 

1.54711 

1.80496  2.022811  2.32066,  2..57851 

.14 

.55537  .83306 

1.1107411.38842 

1.66611 

1.94380  2.221491  2.49917,  2.77630 

.15 

.59504 

.89256 

1.19009 

1.48760 

1.78512 

2.0S264|  2.38017  2.67769 

2.97520 

.16 

.63471 

.95207 

1.26942 

1.58678 

1.90413 

2.22149  2..53884  2.85620 

3.173.55 

.17 

.67438 

1.01157 

1.34876 

1.68595 

2.02314 

2.36033t  2.697.521  3.03471 

3.37190 

.18 

.71405 

1.07107 

1.42810 

1.78512 

2.14215 

2.49917  2.856201  3.21322 

3.57025 

.19 

.75372 

1.13058  1.50744 

1.88430 

2.26116 

2.63802  3.01487 

3..39173 

3.76859 

.30 

.79339 

1.19008' 1.58678 

1.98347 

2.38017 

2.77686  3.17355 

3.57025 

3.96694 

.31 

.83306 

1.24959  1.66611 

2.08264 

2.49917 

2.91570 

3..33223 

3.74876 

4.16529 

.33 

.87273 

1.30909  1.74545 

2.18182 

2.61818 

3.054.55 

3.49091 

3.92727 

4.36363 

.33 

.91240 

1.36859;  1.82479 

2.28099 

2.73719 

3.193.39 

3.64959i  4.10578 

4.50193 

.34 

.95207 

1.42810  1.90413 

2..38016 

2.85620 

3.33223 

3.80826  4.28430 

4.76033 

.35 

.99173 

1.48760  1.98347 

2.47934 

2.97521 

3.47107 

3.96694  4.462811  4.95867 

.36 

1.03140  1.5471li2.08281 

2.57851 

3.09421 

3.60992 

4.125621  4.64132 

5.15702 

.37 

1.07107  1.6066112.14215 

2.67768 

3.21322 

3.74876 

4.28430 

4.81983 

5.35537 

.38 

1.11074  1.6661112.22149 

2.77686 

3.33223 

3.88760 

4.44297 

4.99835 

5.55372 

.39 

1.1.5041  1.72562' 2.30083 

2.87603 

3.45124 

4.02645 

4.60105 

5.17686 

5.75206 

.30 

1.19008  1.78512  2.38017 

2.97520 

3.57025 

4.16529 

4.76033 

5.35537 

5.9.5041 

.31 

1.22975' 1.84463  2.45950 

3.07438 

3.68925 

4.30413 

4.91901 

5.53388 

6.14876 

.33 

1.26942  1.90413  2.53884 

3.17355 

3.80826 

4.442971  5.07769 

5.712401  6.34710 

.33 

1.30909 

1.96364  2.61818 

3.27273 

3.92727 

4.58182 

5.23636 

5.89091 1  6.54545 

.34 

1.34876 

2.0231412.69752 

3.37190 

4.04628 

4.72066 

5.39504 

6.06942,  6.74380 

.35 

1.38843 

2.0826412.77686 

3.47107 

4.16529 

4.85950 

5.55372 

6.247931  6.94215 

.36 

1.42810 

2.1421512.85620 

3,57025 

4.28430 

4.99835 

5.71240 

6.42645!  7.14049 

.37 

1.46777 

2.20165'2.93554 

3.66942 

4.40331 

5.1.3719 

5.87107 

6.604961  7.33884 

.38 

1.50744 

2.26116'3.014S7 

3.76859 

4.52231 

5.27603 

6.02975 

6.78347 

7.53719 

.39 

1.54711 

2..32066'3.09421 

3.86777 

4.64132 

5.41487 

6.18843 

6.96198 

7.73553 

.40 

1.58678 

2.38017 

3.173.55 

3.96694 

4.76033 

5.5.5372 

6.34711 

7.14049 

7.93388 

.41 

1.62645 

2.43967 

3.25289 

4.06611 

4.87934 

5.69256 

6.50578 

7.31901 

8.13223 

.42 

1.66611 

2.49917 

3.33223 

4.16529 

4.99835 

5.83140 

6.66446 

7.49752 

8.33057 

.43 

1.70579 

2.55868 

3.41157 

4.26446 

5.11735 

5.97025 

6.82314 

7.67603 

S.52892 

.44 

1.74545 

2.61818  3.49091 

4.36363 

5.23636 

6.10909 

6.98182 

7.85455 

8.72727 

.45 

1.78512 

2.6776913.57025 

4.46281 

5.35537 

6.24793 

7.14049 

8.03305 

8.92561 

.46 

1.82479 

2.73719  3.649.5914.56198 

5.47438 

6.38678 

7.29917 

8.21157 

9.12396 

.47 

1.86446 

2.7966913.72893 

4.66115 

5.59339 

6.52562 

7.45785 

8.39008 

9.32231 

.48 

1.90413 

2.85620 

3.80826 

4.7()033 

5.71240 

6.66446 

7.616.53 

8.56859 

9.52066 

.49 

1.94380 

2.91570 

3.88760 

4.85950 

5.83140 

6.80331 

7.77521 

8.74711 

9.71900 

0.50 

1.98347 

2.97621 

3.96694 

4.95867 

5.95041 

6.94215 

7.93388 

8.92561 

9.91735 

MEASUREMENT   OF   IRRIGATION    WATER. 


47 


Table   5 — Acre-feet  equivalent   to   a  given  number  of  second-feet 
flowing  for  a  given  length  of  time.     (See  paragraph  22.) 


Days  of  $4  Hours 


10 


02.314  3.03471  4. 

0u2Si  3. 

10248'3. 

1421.5;3, 

18182  3. 


09421 
15372 
21322 
27273  4 
221491 3.33223 1 4 
391734 
45124  4 


261163, 
.30083  3. 
34049' 3. 
3S017i3. 
419S3[3. 
459.50  3, 
4991713. 
53884:3, 
57S5ll3, 
618183, 
657853, 
69752  4, 
737194, 
7768614, 
SI653I4, 
85620  4, 


S95S7 

93554 

97521 

0148714 

05455  4 

09421 

13388 

17355 

21322 

25289 

29256 

33223 

37190 

41157 

45124 

4909115 

53058|5 

57025 1 5 

60992 1 5 

64959'5 

68925,5 

72893  is 


3 
3 
3, 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3, 
3.927: 


768.59  5 
80826 
84793 
88760 

92727 
95694 


51074 

57025 

62975 

68925|4 

74876  4 

.80826 

86777 

92727 

98678 

04628 

10578 

16.529 

22479 

28430 

34380 

40331 

46281 

52231 

58182J6 

64132  6 

70083 

76033 

81983 

87934 

93.SS4 

99S35 

05785 

11735 

17686 

23636 

29587 

35.537 

41487 

47438 

5338S 

59339 

65289 

71240 

77190 

83140 

89091 

95041 


04628  5. 

12562,5. 

204965, 

28430!5, 

36364'5, 

44297J5, 

52231  5, 

601655, 

6S099  5, 

76033  5 

83967!  6 

9190116 

99835 

07769 

15702 

23636 

31570 

39504 

47438 

55372 

63306 

71240 

79173 

87107 

95041 

02975 

10909 

18843 

26777 

34711 

42645 

50578 

58512 

66446 

74380 

82314 

90248 

98182 

06116 

14049 

21983 

29917 

37851 

45785 

53719 

616.53 

69587 

77521 

8.5455 

93388 


05785 
15702 
25619 
35537 
45454 
553721  6 
.65289  6 
.75206 
85124 
95041 
04958 
.14876 
24793 
34710 
.44628 
54545 
64462 
74380 
.84297 
94215 
04132 
.14049 
23907 
,33884 
43801 
53719 
63636 
73553 
83471 
93388 
03305 
13223 
23140 
33057 
42975 
52S92I10 
62809' 10 
72727110 
82644!  10 
92561110 
02479  10 
12396' 10 
22313|11 
32231111, 


,06942 

,18843 

,30744 

,42645 

,54545 

,66446 

,78347 

,90248 

.02149 

.14049 

.25950 

.37851 

.49752 

.61653 

.73554 

.8.5455 

.97355 

.09356 

.21157 

.33058 

.44959 

,56859 

,68760110, 

,80661110, 

,92562110, 

,04463110. 

.16364110. 

,28264  10, 

,401651 10. 

,52066111, 

,63967  11. 

,75868  11. 

,87769!ll. 

,99669!ll. 

,11570  11, 

,2.3471  11. 

,35372  12. 

,47273  12. 

,59173!  12, 

,71074!  12. 

,82975  12. 


08099 
219,83 
35868 
49752 
63636 
77521 
91405 
0.5289 
19173 
33058 
46942 
60826 
74711 
88595ilO, 
02479 1 10 
16364  10, 
30248  10 
.44132  10. 


58016 

71901 

85785 

99669111 

13554  11 

274381 11 

41322,11 


94876 
08777 
18678 


42148 
52066 
619S3 
71900 
81818 
91735 


11.30578113. 

11 

11 

11 

11 

11 


.424  (y 
.54380 
.66281 
.78182 
.90083 


55207 

69091 

82975 

96859 

10744 

24628 

38512 

52397 

66281 

80165113 

940491 13 

079.34113 

218181 13 

35702114 

495871 14, 

63471  14, 

77355!  14 

91240  14, 

05124' 14. 

1900SI15 

328934.5. 


46777 
60661 
74545 
88430 


09256 

25124 

40992 

56859 

72727 

88595 

04463 

20331 

36198 

52066 

67934 

838021 11 

99669  11 

15537  11 

31405:11 

47273  11 

63140  11 

79008112 

94876:12 

10744112 

26611112 

,42479  12 

58347  13 

74215113 

90083,13 

0595013 

21818,13 

37686  13 

53554 

69421 

85289 

01157 

17025 

32893 

48760 

6462S 

80496 

96363 

12231 

28099 

43967 

59835 

75702 

91570 

07438 

23306 

39173 

55041 

70909 

86777 


.10413  10 
.28264  10, 
.46116  la 
.63967110 

8181810 


99669 
17521 
35372 
53223 
71074 
88925 
06777 
24628 
42479 


60331 

.78182 
.96033 
.138,84 
.31735 
.49587 
67438 
85289 
03140 
20992  14 
38843  14 
56694  15 
74.545  15, 
92397  15 
1024815, 
2809915 
4595016 
6380116 
81653!l6 
9950416 
17355!  16, 
35207il7 
53058' 17, 
7090917, 
8876017, 
0661117, 
.24463!  18, 
42314  18 
60165 
78016 
95868 
13719 
31570 
49421 
67273 
85124 


11,570 
.31404 
51939 
.71074 
.90909 
10743 
.30578 
50413 
.70247 
.90082 
.09917 
.29751 
.49586 
.69421 
.892.55 
.09090 
28925 
.48760 
.68594 
88429 
.082t)4 
.28098 
47933 
.67768 
87603 
07437 
27272 
47107 
.66941 
.86770 
.06611 
.26445 
,46280 
,66115 
,85919 
,057,?4 
,25619 
,454.54 
,65288 
85123 
04958 
24792 
44627 
64462 
84297 
04131 
23906 
43801 
63635 
83470 


48 


MEASUREiMKNT   OF   IRRIGATION    WATER. 


Table  6. — Discharge  of  standard  submerged  rectangular  orifices  in 
cubic  feet  per  second,  computed  from  the  formula  Q  =■ 
0.61  yZgH  A.    (See  paragraphs  28  and  34.) 


Head  H, 

Cross-sectional  area  A  of  orifice,  square  feet. 

feet. 

0.35 

0.5 

0.J5 

1.0      j      1.35 

1.5 

1.75 

2.0 

0.01 
.03 
.03 
.04 
.05 
.06 
.07 
.08 
.09 
.10 
.11 
.12 
.13 
.14 
.15 
.16 
.17 
.18 
.19 
.■M 
.21 
.28 
.23 
.U 
.25 
.26 
.27 
.28 
.29 
.30 
..31 
.32 
.33 
.34 
.35 
.30 
.37 
.38 
.30 

0.40 


0.122 

0.245 

0.367 

0.489 

0.611 

0.173 

0.346 

0.518 

0.G91 

0.S04 

0.212 

0.424 

0.635 

0.S47 

1.059 

0.245 

0.489 

0.734 

0.97S 

1.223 

0.273 

0.547 

0.820 

1.093 

1.367 

0.300 

0.599 

0.899 

1.198 

1.497 

0.324 

0.647 

0.971 

1.294 

1.617 

0.346 

0.691 

1.037 

1.383 

1.729 

0.367 

0.734 

1.101 

1.468 

1.835 

0.387 

0.773 

1.160 

1.557 

1.933 

0.406 

0.811 

1.217 

1.622 

2.027 

0.424 

0.847 

1.271 

1.694 

2.118 

0.441 

0.882 

1.323 

1.764 

2.205 

0.458 

0.915 

1.373 

1.830 

2.287 

0.474 

0.947 

1.421 

1.895 

2.369 

0.489 

0:978 

1.467 

1.95G 

2.445 

0.504 

1.008 

1.512 

2.01C 

2.520 

0.519 

1.037 

1.556 

2.075 

2.593 

0.533 

1.066 

1.599 

2.132 

2.605 

0.547 

1.094 

1.641 

2.188 

2.735 

0.561 

1.120 

1.681 

2.241 

2.801 

0.574 

1.148 

1.722 

2.296 

2.870 

0.5S7 

1.172 

1.759 

2.345 

2.931 

0.600 

1.198 

1.797 

2.396 

2.995 

0.612 

1.223 

1.834 

2.446 

3.057 

0.624 

1.247 

1.871 

2.494 

3.117 

0.636 

1.270 

1.906 

2.541 

3.176 

0.646 

1.294 

1.942 

2.589 

3.236 

0.6.59 

1.319 

1.978 

2.638 

3.297 

0.670 

1.339 

2.009 

2.078 

3.347 

0.681 

1.363 

2.045 

2.726 

3.407 

0.C92 

i.3S2 

2.073 

2.704 

3.455 

0.703 

1.405 

2.107 

2.810 

3.513 

0.713 

1.426 

2.139 

2.852 

3.565 

0.724 

1.446 

2.169 

2.892 

3.615 

0.734 

1.467 

2.201 

2.934 

3.667 

0.745 

1.488 

2.232 

2.976 

3.720 

0.754 

1.508 

2.262 

3.016 

3.770 

0.764 

1.527 

2.291 

3.054 

3.818 

0.774 

1.547 

2.321 

3.094 

3.867 

0.734 
1.037 
1.271 
1.468 
1.640 
1.797 
1.941 
2.074 
2.201 
2.320 
2.433 
2.542 
2.645 
2.745 
2.842 
2.934 
3.024 
3.112 
3.198 
3.282 
3.361 
3.464 
3.517 
3.599 
3.668 
3.741 
3.811 
3.883 
3.956 
4.017 
4.089 
4.146 
4.215 
4.278 
4.338 
4.401 
4.464 
4.524 
4.582 
4.641 


0.856 
1.210 
1.483 
1.712 
1.913 
2.097 
2.265 
2.420 
2.638 
2.707 
2.839 
2.965 
3.086 
3.203 
3.316 
3.423 
3.528 
3.631 
3.731 
3.829 
3.921 
4.018 
4.103 
4.193 
4.280 
4.365 
4.446 
4.530 
4.616 
4.687 
4.771 
4.837 
4.917 
4.991 
5.061 
5.135 
5.208 
5.278 
5.345 
5.415 


0.978 
1.382 
1.G94 
1.957 
2.186 
2.396 
2.588 
2.766 
2.935 
3.094 
3.244 
3.389 
3.527 
3.660 
3.790 
3.912 
4.032 
4.150 
4.264 
4.376 
4.482 
4.592 
4.690 
4.792 
4.891 
4.988 
5.082 
5.178 
5.276 
5.356 
5.452 
5.528 
5.620 
5.704 
5.784 
5.868 
5.952 
6.032 
6.109 
0.188 


MEASUREMENT   OF   IRRIGATION   WATER. 


49 


Table  6. — Discharge  of  standard  submerged  rectangular  orfices  in 
cubic  feet  per  second,  computed  from  the  formula  Q  =  0.61 

V2gH  A.    {See  paragraphs  28  and  34.) 


Cross-sectional  area  A  of  orifice, 

square  feet. 

Head  H, 

feet. 

0.35 

0.5 

• 

0.75 

1.0 

l.%5 

1.5 

1.75 

3.0 

0.41 

0.783 

1..567 

2.350 

3.133 

3.917 

4.700 

5.483 

6.2GC 

.43 

0.792 

1.585 

2.377 

3.170 

3.962 

4.754 

5.547 

6.339 

.43 

0.802 

1.604 

2.406 

3.208 

4.010 

4.812 

5.614 

6.416 

.44 

0.811 

1.622 

2.433 

3.244 

4.055 

4.S66 

5.677 

6.488 

.45 

0.820 

1.640 

2.461 

3.281 

4.101 

4.921 

5.741 

6.. 362 

.46 

0.829 

1.659 

2.4*89 

3.318 

4.147 

4.977 

5. 807 

6.636 

.47 

0.839 

1.678 

2.517 

3.356 

4.195 

5.035 

5.874 

6.713 

.48 

0.847 

1.695 

2.542 

3.389 

4.237 

5.084 

5.931 

0.77S 

.49 

0.856 

1.712 

2.568 

3.424 

4.280 

5.136 

5.992 

6.848 

.69 

0.865 

1.729 

2.594 

3.458 

4.323 

5.188 

6.052 

6.917 

.51 

0.873 

1.746 

2.620 

3.493 

4.366 

5.239 

6.112 

6.986 

.53 

0.882 

1.763 

2.645 

3.527 

4.409 

5.290 

6.172 

7.054 

.53 

0.890 

1.780 

2.670 

3.560 

4.451 

5.341 

6.231 

7.121 

.54 

0.898 

1.797 

2.995 

3.593 

4.491 

5.390 

6.288 

7.1S6 

.55 

0.907 

1.813 

2.719 

3.626 

4.533 

5.439 

6.345 

7.252 

.56 

0.915 

1.830 

2.745 

3.660 

4.575 

5.490 

6.405 

7.320 

.57 

0.923 

1.846 

2.769 

3.692 

4.615 

5.538 

6.461 

7.3S4 

.58 

0.931 

1.862 

2.794 

3.723 

4.6.56 

5.587 

6.518 

7.450 

.59 

0.939 

1.879 

2.818 

3.757 

4.997 

5.636 

6.575 

7.514 

.60 

0.947 

1.895 

2.843 

3.790 

4.737 

5.6S4 

6.632 

7.579 

.61 

0.955 

1.910 

2.865 

3.820 

4.775 

5.730 

6.685 

7.640 

.69 

0.963 

1.925 

2.887 

3.850 

4.812 

5.775 

6.737 

7.700 

.63 

0.971 

1.941 

2.911 

3.882 

4.853 

5.823 

6.793 

7.764 

.64 

0.978 

1.956 

2.934 

3.912 

4.,S90 

5.S68 

6.846 

7.824 

•D9 

0.986 

1.972 

2.9.5S 

3.944 

4.930 

5.916 

6.902 

7.888 

0.993 

1.987 

2.980 

3.974 

4.967 

5.960 

6.954 

7.947 

.67 

1.001 

2.C02 

3.003 

4.004 

5.005 

6.006 

7.007 

8.008 

.68 

1.008 

2.016 

3.034 

4.038 

5.040 

6.048 

7.056 

8.064 

.69 

1.016 

2.032 

3.048 

4.064 

5.080 

6.096 

7.112 

8.128 

.70 

1.023 

2.046 

3.069 

4.092 

5.115 

6.138 

7.161 

8.184 

.71 

1.031 

2. 062 

3.093 

4.124 

5.155 

6.186 

7.217 

8.248 

.72 

1.038 

2.076 

3.114 

4.152 

5.190 

6.228 

7.266 

8.304 

.73 

1.045 

2.090 

3.135 

4.180 

5.225 

6.270 

7.315 

8.360 

.74 

1.052 

2.104 

3.158 

4.210 

5.260 

6.311 

7.369 

8.421 

.75 

1.059 

2.118 

3.178 

4.237 

5.296 

6.355 

7.413 

8.475 

.76 

1.066 

2.132 

3.198 

4.264 

5.330 

6.396 

7.462 

8.528 

.77 

1.072    . 

2.145 

3.217 

4.290 

5.362 

6.434 

7.507 

8.579 

.78 

1.080 

2.160 

3.240 

4.320 

5.400 

6.480 

7.560 

8.640 

.79 

1.087 

2.174 

3.261 

4.348 

5.435 

6.522 

7.609 

8.696 

0.80 

1.094 

2.188 

3.282 

4.376 

5.470 

6.564 

7.658 

8.752 

50 


MEASUREMENT   OF   IRRIGATION   WATER. 


Table  7 — Coefficients  C  to  be  applied  to  a  discharge  given  by  Table 
6  to  give  the  discharge  of  the  same  orifice  suppressed,  com- 
puted from  the  formula  C"  =  1  +  0.15  r. 


Size  of  orifice. 

Bottom  suppressed. 

Bottom  and  ndea 
suppressed. 

d,  feet. 

I,  feet. 

A, 
square  feet. 

r 

c' 

(' 

1.0 

0.25 

0.40 

1.06 

0.60 

1.09 

0.35 

2.0 

.50 

.44 

1.07 

.56 

1.08    ' 

3.0 

.75 

.46 

1.07 

.54 

1.08 

1.0 

.50 

.33 

1.05 

.67 

1.10 

1.5 

.75 

.37 

1.06 

.63 

1.09 

0.5 

2.0 

1.00 

.40 

1.06 

.60 

1.09 

2.5 

1.25 

.42 

1.06 

.58 

1.09 

3.0 

1.50 

.43 

1.06 

.57 

1.09 

1.33 

1.00 

.32 

1.05 

.68 

1.10 

1.67 

1.25 

.34 

1.05 

.66 

1.10 

0.75 

2.00 

1.50 

.36 

1.05 

.64 

1.10 

2.33 

1.75 

.38 

1.06 

.62 

1.09 

2.67 

2.00 

0.39 

1.06 

0.61 

1.09 

MEASUREMENT   QP   IRRIGATION    WATER.  51 

Table  8. — Sample  rating  tabic  for  small  Price  current  meter. 


03 

5  Revolu- 
tions. 

10  Revolu- 
tions. 

20  Revolu- 
tions. 

30  Revolu- 
tions. 

40  Revolu- 
tions. 

DO 

o 

Velocity, 

ft.  per 
second. 

Diff. 

Velocity, 
ft.  per 
second. 

Diff, 

Velocity, 
ft.  per 
second. 

Diff. 

Velocity, 
ft.  per     Diff. 
second. 

Velocity, 
ft.  per 
second. 

Diff. 

O  o 

40 
41 
43 
43 
44 
45 
46 

0.316 
.310 
.304 
.298 
.293 
.288 
.283 
.278 
.273 
.268 
.263 
.259 
.255 
.251 
.247 
.243 
.239 
.235 
.232 
.229 

0.226 

.006 
.006 
.006 
.005 
.005 
.005 
005 

0.592 
.578 
..565 
.553 
.542 
.531 
.521 

.014 
.013 
.012 
.011 
.011 
.010 
.010 
.010 
010 
.009 
.008 
.008 
.008 
.008 
.007 
.007 
.007 
.007 
.006 
.006 

1.14 

1.11 

1.08 

1.06 

1.04 

1.02 

1.00 

0.981 
.961 
.942 
.923 
.905 
.888 
.872 
.857 
.842 
.828 
.814 
.801 
.788 
.775 

.03 

.03 

.02 

.02 

.02 

.02 

.02 

.02 

.019 

.019 

.018 

.017 

.016 

.015 

.015 

.014 

.014 

.013 

.013 

,013 

1.69 
1.65 
1.61 
1.57 
1.54 
1.51 
1.48 
1.45 
1.42 
1.39 
1.36 
1..33 
1.30 
1.28 
1.26 
1.24 
1.22 
1.20 
1.18 
1.16 
1.14 

.04 
.04 
.04 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.02 
.02 
.02 
.02 
.02 
.02 
.02 
.02 

2.25 
2.20 
2.15 
2.10 
2.05 
2.00 
1.96 
1.92 
1.88 
1.84 
l.SO 
1.77 
1.74 
1.71 
1.68 
1.65 
1.62 
1.59 
1.56 
1.53 
1.51 

.05 
.05 
.05 
.05 
.05 
.04 
.04 
.04 
.04 
.04 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.03 
.02 

4e 

41 
43 

43; 

44 
45 
46 

47 

4S 
49 
50 
61 
53 
53 
64 
65 
56 
67 
68 
59 
60 

.005 
.005 
.005 
.004 
.004 
.004 
.004 
.004 
.004 
.004 
.003 
.003 
■-003 

.511 
.501 
.491 

.482 
.474 
.466 
.458 
.450 
.443 
.436 
.429 
.422 
.416 
.410 

47 

48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
58 
59 
69 

CD 

50  Revolu- 
tions. 

60  Revolu- 
tions. 

SO  Revolu- 
tions. 

100  Revolu- 
tions. 

150  Revolu- 
tions. 

o 
.S  m 

Velocity, 
ft.  per 
second. 

Diff. 

Velocity, 
ft.  per 
second. 

Diff. 

Velocity, 
ft.  per 
second. 

Diff. 

Velocity, 
ft.  per 
second. 

Diff. 

Velocity, 
ft.  per 
second. 

Diff. 

o 

40 
41 
43 
43 
44 
45 
46 
47 
48 
49 
60 
51 
Bit 
53 
54 
65 
56 
67 
68 
69 
60 

2.80 
2.73 
2.67 
2.61 
2.55 
2.50 
2.45 
2.40 
2.35 
2.30 
2.25 
2.21 
2.17 
2.13 
2.09 
2.05 
2.01 
1.97 
1.94 
1.91 
1.88 

.07 
.06 
.06 
.06 
.05 
.05 
.05 
.05 
.05 
.05 
.04 
.04 
.04 
.04 
.04 
.04 
.04 
.03 
.03 
.03 

3.36 
3.28 
3.20 
3.13 
3.06 
2.99 
2.92 
2.86 
2.80 
2.74 
2.69 
2.64 
2.59 
2.54 
2.49 
2.45 
2.41 
2  37 
2.33 
2.29 
2.25 

.08 
.08 
.07 
.07 
.07 
.07 
.06 
.06 
.06 
.05 
.05 
.05 
.05 
.05 
.04 
.04 
.04 
.04 
.04 
.04 

4.47 
4.36 
4.26 
4.16 
4.06 
3.97 
3.89 
3.81 
3.73 
3.65 
3.58 
3.51 
3.45 
3.39 
3.33 
3.27 
3.21 
3.15 
3.09 
3.04 
2.99 

.11 
.10 
.10 
.10 
.09 
.08 
.08 
.08 
.08 
.07 
.07 
.06 
.06 
.06 
.06 
.06 
.06 
.06 
.05 
.05 

5.57 
5.43 
5.30 
5.18 
5.07 
4.96 
4.85 
4.75 
4.65 
4.56 
4.47 
4.38 
4.30 
4.22 
4.14 
4.07 
4.00 
3.93 
3.86 
3.80 
3.74 

.14 
.13 
.12 
.11 
.11 
.11 
.10 
•1.0 
.09 
.09 
.09 
.08 
.08 
.08 
.07 
.07 
.07 
.07 
.06 
.00 

8.35 
S.15 
7.96 
7.78 
7.61 
7.44 
7.28 
7.12 
6.97 
6.82 
6.68 
6.55 
6.43 
6.31 
6.19 
6.08 
5.97 
5.87 
5.77 
5.67 
5..57 

.20 
.19 
.18 
.18 
.17 
.16 
.16 
.15 
.14 
.14 
.13 
.12 
.12 
.12 
.11 
.11 
.10 
.10 
.10 
.10 

40 

41 

43 

43 

44 

45 

46 

47  • 

48 

49 

50 

61 

63 

53 

54 

55 

56 

57 

63 

59 

BO 

52 


MEASUREMENT   OP    IRRIGATION   WATER. 


Table  9 — Sample  table  of  current  tneter  notes  and  computations, 
by  formula  (18),  for  U.  S.  Reclamation  Service  Power  Canal 
at  Spanish  Fork,  Utah. 

UNITED   STATES   RECLAMATIOlSr    SERVICE 

Current  Meter  Notes 

Date,  Sept.  17,  1909,  10.30  A.  M.;  Stream,  U.  S.  R.  S.  Power  Canal; 
Party,  E.  S.  Fuller;  Locality,  Spanish  Fork,  Utah,  Meter  No.  400 
Gage  height,  beg.  2.80,  end  3.80,  mean  2.80.  Total  area  19.0;  Mean 
velocity,  5.66;  Discharge,  107. 


Observations. 

Com 

putatioas. 

Dist. 

Depth 

Depth 
of  ob- 
servat. 

Time 
in  sec- 
onds 

Rev- 
olu- 
tions 

Velocity. 

Mean 
depth 

Width 

Area 

from 

initial 

point 

At 
point 

Mean 
in  ver- 
tical 

Mean 
in  sec- 
tion 

Dis- 

cliaTKc 

4.2 

0 

1.4 

2.8 

Est. 

.8 

.56 
2.24 

.56 
2.24 

.56 
2.24 

.56 
2.24 

.56 
2.24 

.8 
Est. 

3.49 
4.98 
6.64 
5.20 
6.49 
6.05 
6.32 
5.72 
6.12 
5.61 
6.02 
5.27 
4.87 
3.41 

3.49 
4.98 

5.92 

6.27 

6.02 

6.86 

5.64 
4.87 
3.41 

5.6 

7.0 

46.0 
34.4 
44.0 
35.2 
37.8 
36.2 
40.0 
37.4 
40.8 
38.0 
43.4 
47.0 

100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 

4.24 
5.45 

.7 
2.1 

1.4 
1.4 

0.98 
2.94 

4.2 
16.0 

8.0 

2.8 

6.10 

2.8 

1.0 

2.80 

17.1 

9.0 

2.8 



6.14 

2.8 

1.0 

2.80 

17.2 

10.0 

2.8 

6.94 

2.8 

1.0 

2.80 

16.6 

ii.o 

2.8 

5.75 

2.S 

1.0 

2.80 

16.1 

12.4 
13.8 

1.4 
0 

5.26 
4.14 
6.62 

2.1 
.7 

1.4 
1.4 

2.94 
0.98 
lfl.04 

16.4 
4.1 

100.7 

MEASUREMENT    OF    IRRIGATION    WATER. 


53 


Table    10 — Sample   rating    table   for    U.    S.    Reclamation    Service 
Power  Canal  at  Spanish  Fork,  Utah. 


Gage  height. 

Discharge. 

Difference. 

Gage  height. 

Discharge. 

DiSereuce. 

Feet. 

Scc.-ft. 

Sec.-ft. 

Feet. 

Sec.-ft. 

Sec. -It. 

0.0 

0.0 

0.2 

2.1 

60.1 

5.9 

.1 

0.2 

0.5 

.2 

66.0 

6.2 

.2 

0.7 

0.8 

.3 

72.2 

6.5 

.3 

1.5 

1.1 

.4 

78.7 

6.8 

.4 

2.6 

1.4 

.5 

85.5 

7.0 

.5 

4.0 

1.7 

.6 

92.5 

7.2 

.6 

5.7 

1.9 

.7 

99.7 

7.3 

.7 

7.6 

2.1 

.8 

107 

8 

.8 

9.7 

2.3 

.9 

115 

S 

.9 

12.0 

2.5 

3.0 

123 

8 

1.0 

14.5 

2.7 

.1 

131 

8 

.1 

17.2 

3.0 

.2 

139 

9 

.8 

20.2 

3.3 

.3 

148 

9 

.3 

23.5 

3.5 

.4 

157 

9 

.-1 

27.0 

3.8 

.5 

166 

9 

.5 

30.8 

4.1 

.6 

175 

9 

.6 

34.9 

4.4 

.7 

184 

9 

.7 

39.3 

4.7 

.8 

193 

9 

S 

44.0 

5.1 

.9 

202 

9 

.9 

49.1 

5.4 

4.0 

211 

2.0 

54.5 

5.6 

o 


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